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  • Do you use enums in your data applications and how?

    - by Ivan
    My practice shows that a general enterprise application has a lot of entities which's nature corresponds to an elementary enumeration. For example We may have an Order entity which may have such fields as "OrderType", "OrderStatus", "Currency", etc. referencing corresponding Entities which are nothing more than just a textual name bound to a key to be referenced. Using enums would look very natural here. But entities have to be defined in application code at design-time, am I right? While in we need to be able to CRUD enum value variants at runtime and use enums in server-side SQL queries (like stored procedures and views). What are you practices and thoughts on this subject? I am particularly interested in C#4, linq and T-SQL.

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  • How to increase signal/range of your Wi-Fi antenna-less repeater/booster over the network?

    - by kenorb
    I've BT Home Hub in the upper flat (2-3 walls behind) and I'm using WPS Wireless-N Wifi Range Router Repeater Extender in my flat where I'm using my laptop. These are antenna-less devices. Are there any life-hack tricks to increase signal/range of my repeater without buying the new more powerful repeater? I've tried already to move my repeater closer to the ceiling or putting the aluminium foil underneath, but it didn't help. Are there any methods, specific plates or materials which can boost the signal? Specification: Model: WN518W2 Frequency range: 2.4-2.4835GHz Wireless transmit power: 14 ~17 dBm (Typical) Wireless Signal Rates With Automatic Fallback: 11n: Up to 300Mbps(dynamic), 11g: Up to 54Mbps(dynamic), 11b: Up to 11Mbps(dynamic) Modulation Technology: DBPSK, DQPSK, CCK, OFDM, 16-QAM, 64-QAM Receiver Sensitivity: 300M: -68dBm@10% PER / 150M: -68dBm@10% PER / 108M: -68dBm@10% PER / 54M: -68dBm@10% PER / 11M: -85dBm@8% PER / 6M: -88dBm@10% PER / 1M: -90dBm@8% PER Product dimensions: 11 * 6 * 7cm

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  • Entity Aspect (in Spring)

    - by niklassaers
    Hi guys, I'm having a bit of a problem defining my aspects. I've got a bunch of entities that I'd like to profile the get-methods in, so I've written the following pointcut and method @Pointcut("execution(* tld.myproject.data.entities.*.get*()") public void getEntityProperty() {} @Around("getEntityProperty()") public Object profileGetEntityProperty(ProceedingJoinPoint pjp) throws Throwable { long start = System.currentTimeMillis(); String name = pjp.getSignature().getName(); Object output = pjp.proceed(); long elapsedTime = System.currentTimeMillis() - start; if(elapsedTime > 100) System.err.println("profileGetEntityProperty: Entity method " + name + " execution time: " + elapsedTime + " ms."); return output; } I've got weaving turned on in my configuration, and aspects weaving into the business layer work just fine. Is my pointcut correctly written? Or is there something about entities that make them non-weavable? (my entity is prefixed with @Entity before the class definition) Cheers Nik

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  • Is multi-level polymorphism possible in SQLAlchemy?

    - by Jace
    Is it possible to have multi-level polymorphism in SQLAlchemy? Here's an example: class Entity(Base): __tablename__ = 'entities' id = Column(Integer, primary_key=True) created_at = Column(DateTime, default=datetime.utcnow, nullable=False) entity_type = Column(Unicode(20), nullable=False) __mapper_args__ = {'polymorphic_on': entity_type} class File(Entity): __tablename__ = 'files' id = Column(None, ForeignKey('entities.id'), primary_key=True) filepath = Column(Unicode(255), nullable=False) file_type = Column(Unicode(20), nullable=False) __mapper_args__ = {'polymorphic_identity': u'file', 'polymorphic_on': file_type) class Image(File): __mapper_args__ = {'polymorphic_identity': u'image'} __tablename__ = 'images' id = Column(None, ForeignKey('files.id'), primary_key=True) width = Column(Integer) height = Column(Integer) When I call Base.metadata.create_all(), SQLAlchemy raises the following error: NotImplementedError: Can't generate DDL for the null type IntegrityError: (IntegrityError) entities.entity_type may not be NULL. This error goes away if I remove the Image model and the polymorphic_on key in File. What gives? (Edited: the exception raised was wrong.)

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  • How to implement multi relationship in SQL Server?

    - by Ethan
    I’m trying to design a database to use with ASP.net MVC application. Here is the scenario: There are three entities and users can post their comments for each of these different entities. I just wonder how just put one table for Comments and link all other entities to it. Obviously, Comments table needs 3 references (foreign key) to those tables but as you know these foreign keys can’t be null and just one of them can be filled for each row. Is there any better way than implementing three different tables for each entity’s comments?

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  • Summarize object area with a Hash in Ruby

    - by Arto Uusikangas
    require 'sketchup' entities = Sketchup.active_model.entities summa = Hash.new for face in entities next unless face.kind_of? Sketchup::Face if (face.material) summa[face.material.display_name] += face.area end end Im trying to get the structure in the array as such: summa { "Bricks" = 500, "Planks" = 4000 } Making a ruby script for Google Sketchup btw But if I run this code i only get Error: #+' for nil:NilClass> C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:17 C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:14:ineach' C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:14 C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:8:in `call' As im used to using PHP and just doing $array['myownassoc'] += bignumber; But i guess this isnt the right approach when using Ruby? So any help in how i need to go would be nice.

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  • How to modify posted form data within controller action before sending to view?

    - by Gary
    I want to render the same view after a successful action (rather than use RedirectToAction), but I need to modify the model data that is rendered to that view. The following is a contrived example that demonstrates two methods that that do not work: [AcceptVerbs("POST")] public ActionResult EditProduct(int id, [Bind(Include="UnitPrice, ProductName")]Product product) { NORTHWNDEntities entities = new NORTHWNDEntities(); if (ModelState.IsValid) { var dbProduct = entities.ProductSet.First(p => p.ProductID == id); dbProduct.ProductName = product.ProductName; dbProduct.UnitPrice = product.UnitPrice; entities.SaveChanges(); } /* Neither of these work */ product.ProductName = "This has no effect"; ViewData["ProductName"] = "This has no effect either"; return View(product); } Does anyone know what the correct method is for accomplishing this?

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  • Querying my JPA provider (Hibernate) for a collection of <Id,Name> of an entity

    - by Ittai
    Hi, I have an entity which looks something like this: Id (PK) Name Other business properties and associations... I have the need for my DAL (JPA with hibernate as provider) to return a list of the entities which correlate to some constraints (or just return them all) but instead of returning the entities themselves I'd like to receive only the Id and the Name properties. I know this can be achieved with HQL/SQL (something like: select id,name from entity where...) but I don't want to go down that road. I was thinking of somehow defining the pair a compositioned part of the entity and thought that might help me but I'm not sure that's "legal" as the Id is the PK. The logic for this scenario is to have a textbox which asynchronously queries the web-service (and through it the DAL) for the relevant entities and once an entity is selected then it is loaded as a whole and shipped to the front-end. Would appreciate any feedback, Ittai

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  • forward all ports via htaccess to new address

    - by user875933
    I have a chat server running on my local machine that listens to different ports. I want to use the sub-domain of one of my accounts to access it. I intend to manually change the redirect whenever my local machine gets a different ip address. So: chat.example.com:123 would redirect to dynamic.ip.address:123 I am trying to accomplish this with .htaccess and RewriteRule I have tried: RewriteEngine on RewriteRule ^(.*) http://dynamic.ip.address/ [L, R=302] but this doesn't work. When I try chat.example.com:123 nothing happens. When I input chat.example.com into the web browser, I get dynamic.ip.address Is .htaccess the right tool for this? I am using a simple web host that gives me ssh access, but not much more.

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  • help with accessing an array/object

    - by noname
    i have printed out the contents of an array/object (named 'document') with print_r. it looks like this: Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [id] => 7006276 ) [name] => Arnessysla [type] => region [latitude] => 64.5833 [longitude] => -21.8833 [entities] => SimpleXMLElement Object ( ) ) ) how do i get the 'entities' contents? i've tried this: $document[0]-attributes['entities'] but it didnt work!

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  • Entity Framework 4 Hiding Underlying Resolver Tables when model is generated from database

    - by grrrrrrrrrrrrr
    When creating an entity framework model from scratch it is possible to specify a Many to Many relationship in the model. e.g Entity1 * ----- * Entity2 When a database is then generated from this, a resolver table is then created automatically between the two entities, this is hidden in the code model, allowing direct access to each of the entities via properties. e.g. Entity1 ----* ResolverEntity *----- Entity2 My question is, when a model is generated from an existing database, which contains resolver tables, is it possible to create the same effect so the resolver tables do not appear in the generated object model? When I have attempted this, the entity framework appears to create entities in the model for the resolver tables with no obvious way of hiding them in the object model. Thanks.

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  • How to model a relationship that NHibernate (or Hibernate) doesn’t easily support

    - by MylesRip
    I have a situation in which the ideal relationship, I believe, would involve Value Object Inheritance. This is unfortunately not supported in NHibernate so any solution I come up with will be less than perfect. Let’s say that: “Item” entities have a “Location” that can be in one of multiple different formats. These formats are completely different with no overlapping fields. We will deal with each Location in the format that is provided in the data with no attempt to convert from one format to another. Each Item has exactly one Location. “SpecialItem” is a subtype of Item, however, that is unique in that it has exactly two Locations. “Group” entities aggregate Items. “LocationGroup” is as subtype of Group. LocationGroup also has a single Location that can be in any of the formats as described above. Although I’m interested in Items by Group, I’m also interested in being able to find all items with the same Location, regardless of which group they are in. I apologize for the number of stipulations listed above, but I’m afraid that simplifying it any further wouldn’t really reflect the difficulties of the situation. Here is how the above could be diagrammed: Mapping Dilemma Diagram: (http://www.freeimagehosting.net/uploads/592ad48b1a.jpg) (I tried placing the diagram inline, but Stack Overflow won't allow that until I have accumulated more points. I understand the reasoning behind it, but it is a bit inconvenient for now.) Hmmm... Apparently I can't have multiple links either. :-( Analyzing the above, I make the following observations: I treat Locations polymorphically, referring to the supertype rather than the subtype. Logically, Locations should be “Value Objects” rather than entities since it is meaningless to differentiate between two Location objects that have all the same values. Thus equality between Locations should be based on field comparisons, not identifiers. Also, value objects should be immutable and shared references should not be allowed. Using NHibernate (or Hibernate) one would typically map value objects using the “component” keyword which would cause the fields of the class to be mapped directly into the database table that represents the containing class. Put another way, there would not be a separate “Locations” table in the database (and Locations would therefore have no identifiers). NHibernate (or Hibernate) do not currently support inheritance for value objects. My choices as I see them are: Ignore the fact that Locations should be value objects and map them as entities. This would take care of the inheritance mapping issues since NHibernate supports entity inheritance. The downside is that I then have to deal with aliasing issues. (Meaning that if multiple objects share a reference to the same Location, then changing values for one object’s Location would cause the location to change for other objects that share the reference the same Location record.) I want to avoid this if possible. Another downside is that entities are typically compared by their IDs. This would mean that two Location objects would be considered not equal even if the values of all their fields are the same. This would be invalid and unacceptable from the business perspective. Flatten Locations into a single class so that there are no longer inheritance relationships for Locations. This would allow Locations to be treated as value objects which could easily be handled by using “component” mapping in NHibernate. The downside in this case would be that the domain model becomes weaker, more fragile and less maintainable. Do some “creative” mapping in the hbm files in order to force Location fields to be mapped into the containing entities’ tables without using the “component” keyword. This approach is described by Colin Jack here. My situation is more complicated than the one he describes due to the fact that SpecialItem has a second Location and the fact that a different entity, LocatedGroup, also has Locations. I could probably get it to work, but the mappings would be non-intuitive and therefore hard to understand and maintain by other developers in the future. Also, I suspect that these tricky mappings would likely not be possible using Fluent NHibernate so I would use the advantages of using that tool, at least in that situation. Surely others out there have run into similar situations. I’m hoping someone who has “been there, done that” can share some wisdom. :-) So here’s the question… Which approach should be preferred in this situation? Why?

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  • One database or many?

    - by dsims
    I am developing a website that will manage data for multiple entities. No data is shared between entities, but they may be owned by the same customer. A customer may want to manage all their entities from a single "dashboard". So should I have one database for everything, or keep the data seperated into individual databases? Is there a best-practice? What are the positives/negatives for having a: database for the entire site (entity has a "customerID", data has "entityID") database for each customer (data has "entityID") database for each entity (relation of database to customer is outside of database) Multiple databases seems like it would have better performance (fewer rows and joins) but may eventually become a maintenance nightmare.

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  • Announcing ASP.NET MVC 3 (Release Candidate 2)

    - by ScottGu
    Earlier today the ASP.NET team shipped the final release candidate (RC2) for ASP.NET MVC 3.  You can download and install it here. Almost there… Today’s RC2 release is the near-final release of ASP.NET MVC 3, and is a true “release candidate” in that we are hoping to not make any more code changes with it.  We are publishing it today so that people can do final testing with it, let us know if they find any last minute “showstoppers”, and start updating their apps to use it.  We will officially ship the final ASP.NET MVC 3 “RTM” build in January. Works with both VS 2010 and VS 2010 SP1 Beta Today’s ASP.NET MVC 3 RC2 release works with both the shipping version of Visual Studio 2010 / Visual Web Developer 2010 Express, as well as the newly released VS 2010 SP1 Beta.  This means that you do not need to install VS 2010 SP1 (or the SP1 beta) in order to use ASP.NET MVC 3.  It works just fine with the shipping Visual Studio 2010.  I’ll do a blog post next week, though, about some of the nice additional feature goodies that come with VS 2010 SP1 (including IIS Express and SQL CE support within VS) which make the dev experience for both ASP.NET Web Forms and ASP.NET MVC even better. Bugs and Perf Fixes Today’s ASP.NET MVC 3 RC2 build contains many bug fixes and performance optimizations.  Our latest performance tests indicate that ASP.NET MVC 3 is now faster than ASP.NET MVC 2, and that existing ASP.NET MVC applications will experience a slight performance increase when updated to run using ASP.NET MVC 3. Final Tweaks and Fit-N-Finish In addition to bug fixes and performance optimizations, today’s RC2 build contains a number of last-minute feature tweaks and “fit-n-finish” changes for the new ASP.NET MVC 3 features.  The feedback and suggestions we’ve received during the public previews has been invaluable in guiding these final tweaks, and we really appreciate people’s support in sending this feedback our way.  Below is a short-list of some of the feature changes/tweaks made between last month’s ASP.NET MVC 3 RC release and today’s ASP.NET MVC 3 RC2 release: jQuery updates and addition of jQuery UI The default ASP.NET MVC 3 project templates have been updated to include jQuery 1.4.4 and jQuery Validation 1.7.  We are also excited to announce today that we are including jQuery UI within our default ASP.NET project templates going forward.  jQuery UI provides a powerful set of additional UI widgets and capabilities.  It will be added by default to your project’s \scripts folder when you create new ASP.NET MVC 3 projects. Improved View Scaffolding The T4 templates used for scaffolding views with the Add-View dialog now generates views that use Html.EditorFor instead of helpers such as Html.TextBoxFor. This change enables you to optionally annotate models with metadata (using data annotation attributes) to better customize the output of your UI at runtime. The Add View scaffolding also supports improved detection and usage of primary key information on models (including support for naming conventions like ID, ProductID, etc).  For example: the Add View dialog box uses this information to ensure that the primary key value is not scaffold as an editable form field, and that links between views are auto-generated correctly with primary key information. The default Edit and Create templates also now include references to the jQuery scripts needed for client validation.  Scaffold form views now support client-side validation by default (no extra steps required).  Client-side validation with ASP.NET MVC 3 is also done using an unobtrusive javascript approach – making pages fast and clean. [ControllerSessionState] –> [SessionState] ASP.NET MVC 3 adds support for session-less controllers.  With the initial RC you used a [ControllerSessionState] attribute to specify this.  We shortened this in RC2 to just be [SessionState]: Note that in addition to turning off session state, you can also set it to be read-only (which is useful for webfarm scenarios where you are reading but not updating session state on a particular request). [SkipRequestValidation] –> [AllowHtml] ASP.NET MVC includes built-in support to protect against HTML and Cross-Site Script Injection Attacks, and will throw an error by default if someone tries to post HTML content as input.  Developers need to explicitly indicate that this is allowed (and that they’ve hopefully built their app to securely support it) in order to enable it. With ASP.NET MVC 3, we are also now supporting a new attribute that you can apply to properties of models/viewmodels to indicate that HTML input is enabled, which enables much more granular protection in a DRY way.  In last month’s RC release this attribute was named [SkipRequestValidation].  With RC2 we renamed it to [AllowHtml] to make it more intuitive: Setting the above [AllowHtml] attribute on a model/viewmodel will cause ASP.NET MVC 3 to turn off HTML injection protection when model binding just that property. Html.Raw() helper method The new Razor view engine introduced with ASP.NET MVC 3 automatically HTML encodes output by default.  This helps provide an additional level of protection against HTML and Script injection attacks. With RC2 we are adding a Html.Raw() helper method that you can use to explicitly indicate that you do not want to HTML encode your output, and instead want to render the content “as-is”: ViewModel/View –> ViewBag ASP.NET MVC has (since V1) supported a ViewData[] dictionary within Controllers and Views that enables developers to pass information from a Controller to a View in a late-bound way.  This approach can be used instead of, or in combination with, a strongly-typed model class.  The below code demonstrates a common use case – where a strongly typed Product model is passed to the view in addition to two late-bound variables via the ViewData[] dictionary: With ASP.NET MVC 3 we are introducing a new API that takes advantage of the dynamic type support within .NET 4 to set/retrieve these values.  It allows you to use standard “dot” notation to specify any number of additional variables to be passed, and does not require that you create a strongly-typed class to do so.  With earlier previews of ASP.NET MVC 3 we exposed this API using a dynamic property called “ViewModel” on the Controller base class, and with a dynamic property called “View” within view templates.  A lot of people found the fact that there were two different names confusing, and several also said that using the name ViewModel was confusing in this context – since often you create strongly-typed ViewModel classes in ASP.NET MVC, and they do not use this API.  With RC2 we are exposing a dynamic property that has the same name – ViewBag – within both Controllers and Views.  It is a dynamic collection that allows you to pass additional bits of data from your controller to your view template to help generate a response.  Below is an example of how we could use it to pass a time-stamp message as well as a list of all categories to our view template: Below is an example of how our view template (which is strongly-typed to expect a Product class as its model) can use the two extra bits of information we passed in our ViewBag to generate the response.  In particular, notice how we are using the list of categories passed in the dynamic ViewBag collection to generate a dropdownlist of friendly category names to help set the CategoryID property of our Product object.  The above Controller/View combination will then generate an HTML response like below.    Output Caching Improvements ASP.NET MVC 3’s output caching system no longer requires you to specify a VaryByParam property when declaring an [OutputCache] attribute on a Controller action method.  MVC3 now automatically varies the output cached entries when you have explicit parameters on your action method – allowing you to cleanly enable output caching on actions using code like below: In addition to supporting full page output caching, ASP.NET MVC 3 also supports partial-page caching – which allows you to cache a region of output and re-use it across multiple requests or controllers.  The [OutputCache] behavior for partial-page caching was updated with RC2 so that sub-content cached entries are varied based on input parameters as opposed to the URL structure of the top-level request – which makes caching scenarios both easier and more powerful than the behavior in the previous RC. @model declaration does not add whitespace In earlier previews, the strongly-typed @model declaration at the top of a Razor view added a blank line to the rendered HTML output. This has been fixed so that the declaration does not introduce whitespace. Changed "Html.ValidationMessage" Method to Display the First Useful Error Message The behavior of the Html.ValidationMessage() helper was updated to show the first useful error message instead of simply displaying the first error. During model binding, the ModelState dictionary can be populated from multiple sources with error messages about the property, including from the model itself (if it implements IValidatableObject), from validation attributes applied to the property, and from exceptions thrown while the property is being accessed. When the Html.ValidationMessage() method displays a validation message, it now skips model-state entries that include an exception, because these are generally not intended for the end user. Instead, the method looks for the first validation message that is not associated with an exception and displays that message. If no such message is found, it defaults to a generic error message that is associated with the first exception. RemoteAttribute “Fields” -> “AdditionalFields” ASP.NET MVC 3 includes built-in remote validation support with its validation infrastructure.  This means that the client-side validation script library used by ASP.NET MVC 3 can automatically call back to controllers you expose on the server to determine whether an input element is indeed valid as the user is editing the form (allowing you to provide real-time validation updates). You can accomplish this by decorating a model/viewmodel property with a [Remote] attribute that specifies the controller/action that should be invoked to remotely validate it.  With the RC this attribute had a “Fields” property that could be used to specify additional input elements that should be sent from the client to the server to help with the validation logic.  To improve the clarity of what this property does we have renamed it to “AdditionalFields” with today’s RC2 release. ViewResult.Model and ViewResult.ViewBag Properties The ViewResult class now exposes both a “Model” and “ViewBag” property off of it.  This makes it easier to unit test Controllers that return views, and avoids you having to access the Model via the ViewResult.ViewData.Model property. Installation Notes You can download and install the ASP.NET MVC 3 RC2 build here.  It can be installed on top of the previous ASP.NET MVC 3 RC release (it should just replace the bits as part of its setup). The one component that will not be updated by the above setup (if you already have it installed) is the NuGet Package Manager.  If you already have NuGet installed, please go to the Visual Studio Extensions Manager (via the Tools –> Extensions menu option) and click on the “Updates” tab.  You should see NuGet listed there – please click the “Update” button next to it to have VS update the extension to today’s release. If you do not have NuGet installed (and did not install the ASP.NET MVC RC build), then NuGet will be installed as part of your ASP.NET MVC 3 setup, and you do not need to take any additional steps to make it work. Summary We are really close to the final ASP.NET MVC 3 release, and will deliver the final “RTM” build of it next month.  It has been only a little over 7 months since ASP.NET MVC 2 shipped, and I’m pretty amazed by the huge number of new features, improvements, and refinements that the team has been able to add with this release (Razor, Unobtrusive JavaScript, NuGet, Dependency Injection, Output Caching, and a lot, lot more).  I’ll be doing a number of blog posts over the next few weeks talking about many of them in more depth. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • Explain Model View Controller

    - by Channel72
    My experience with developing dynamic websites is limited mostly to Java servlets. I've used Tomcat to develop various Java servlets, and I wouldn't hesitate to say that I'm reasonably proficient with this technology, as well as with client-side HTML/CSS/Javascript for the front-end. When I think "dynamic website", I think: user requests a URL with a query string, server receives the query, and then proceeds to output HTML dynamically in order to respond to the query. This often involves communication with a database in order to fetch requested data for display. This is basically the idea behind the doGet method of a Java HttpServlet. But these days, I'm hearing more and more about newer frameworks such as Django and Ruby on Rails, all of which take advantage of the "Model View Controller" architecture. I've read various articles which explain MVC, but I'm having trouble really understanding the benefits. I understand that the general idea is to separate business logic from UI logic, but I fail to see how this is anything really different from normal web programming. Web programming, by it's very nature, forces you to separate business logic (back-end server-side programming) from UI programming (client-side HTML or Javascript), because the two exist in entirely different spheres of programming. Question: What does MVC offer over something like a Java servlet, and more importantly, what exactly is MVC and how is it different from what you would normally do to develop a dynamic website using a more traditional approach such as a Java servlet (or even something older like CGI). If possible, when explaining MVC, please provide an example which illustrates how MVC is applied to the web development process, and how it is beneficial.

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  • July, the 31 Days of SQL Server DMO’s – Day 28 (sys.dm_db_stats_properties)

    - by Tamarick Hill
    The sys.dm_db_stats_properties Dynamic Management Function returns information about the statistics that are currently on your database objects. This function takes two parameters, an object_id and a stats_id. Let’s have a look at the result set from this function against the AdventureWorks2012.Sales.SalesOrderHeader table. To obtain the object_id and stats_id I will use a CROSS APPLY with the sys.stats system table. SELECT sp.* FROM sys.stats s CROSS APPLY sys.dm_db_stats_properties(s.object_id, s.Stats_id) sp WHERE sp.object_id = object_id('Sales.SalesOrderHeader') The first two columns returned by this function are the object_id and the stats_id columns. The next column, ‘last_updated’, gives you the date and the time that a particular statistic was last updated. The next column, ‘rows’, gives you the total number of rows in the table as of the last statistic update date. The ‘rows_sampled’ column gives you the number of rows that were sampled to create the statistic. The ‘steps’ column represents the number of specific value ranges from the statistic histogram. The ‘unfiltered_rows’ column represents the number of rows before any filters are applied. If a particular statistic is not filtered, the ‘unfiltered_rows’ column will always equal the ‘rows’ column. Lastly we have the ‘modification_counter’ column which represents the number of modification to the leading column in a given statistic since the last time the statistic was updated. Probably the most important column from this Dynamic Management Function is the ‘last_updated’ column. You want to always ensure that you have accurate and updated statistics on your database objects. Accurate statistics are vital for the query optimizer to generate efficient and reliable query execution plans. Without accurate and updated statistics, the performance of your SQL Server would likely suffer. For more information about this Dynamic Management Function, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/jj553546.aspx Folllow me on Twitter @PrimeTimeDBA

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  • Unable to cast transparent proxy to type &lt;type&gt;

    - by Rick Strahl
    This is not the first time I've run into this wonderful error while creating new AppDomains in .NET and then trying to load types and access them across App Domains. In almost all cases the problem I've run into with this error the problem comes from the two AppDomains involved loading different copies of the same type. Unless the types match exactly and come exactly from the same assembly the typecast will fail. The most common scenario is that the types are loaded from different assemblies - as unlikely as that sounds. An Example of Failure To give some context, I'm working on some old code in Html Help Builder that creates a new AppDomain in order to parse assembly information for documentation purposes. I create a new AppDomain in order to load up an assembly process it and then immediately unload it along with the AppDomain. The AppDomain allows for unloading that otherwise wouldn't be possible as well as isolating my code from the assembly that's being loaded. The process to accomplish this is fairly established and I use it for lots of applications that use add-in like functionality - basically anywhere where code needs to be isolated and have the ability to be unloaded. My pattern for this is: Create a new AppDomain Load a Factory Class into the AppDomain Use the Factory Class to load additional types from the remote domain Here's the relevant code from my TypeParserFactory that creates a domain and then loads a specific type - TypeParser - that is accessed cross-AppDomain in the parent domain:public class TypeParserFactory : System.MarshalByRefObject,IDisposable { …/// <summary> /// TypeParser Factory method that loads the TypeParser /// object into a new AppDomain so it can be unloaded. /// Creates AppDomain and creates type. /// </summary> /// <returns></returns> public TypeParser CreateTypeParser() { if (!CreateAppDomain(null)) return null; /// Create the instance inside of the new AppDomain /// Note: remote domain uses local EXE's AppBasePath!!! TypeParser parser = null; try { Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); } catch (Exception ex) { this.ErrorMessage = ex.GetBaseException().Message; return null; } return parser; } private bool CreateAppDomain(string lcAppDomain) { if (lcAppDomain == null) lcAppDomain = "wwReflection" + Guid.NewGuid().ToString().GetHashCode().ToString("x"); AppDomainSetup setup = new AppDomainSetup(); // *** Point at current directory setup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory; //setup.PrivateBinPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "bin"); this.LocalAppDomain = AppDomain.CreateDomain(lcAppDomain,null,setup); // Need a custom resolver so we can load assembly from non current path AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve); return true; } …} Note that the classes must be either [Serializable] (by value) or inherit from MarshalByRefObject in order to be accessible remotely. Here I need to call methods on the remote object so all classes are MarshalByRefObject. The specific problem code is the loading up a new type which points at an assembly that visible both in the current domain and the remote domain and then instantiates a type from it. This is the code in question:Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); The last line of code is what blows up with the Unable to cast transparent proxy to type <type> error. Without the cast the code actually returns a TransparentProxy instance, but the cast is what blows up. In other words I AM in fact getting a TypeParser instance back but it can't be cast to the TypeParser type that is loaded in the current AppDomain. Finding the Problem To see what's going on I tried using the .NET 4.0 dynamic type on the result and lo and behold it worked with dynamic - the value returned is actually a TypeParser instance: Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; object objparser = this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); // dynamic works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // casting fails parser = (TypeParser)objparser; So clearly a TypeParser type is coming back, but nevertheless it's not the right one. Hmmm… mysterious.Another couple of tries reveal the problem however:// works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // c:\wwapps\wwhelp\wwReflection20.dll (Current Execution Folder) string info3 = typeof(TypeParser).Assembly.CodeBase; // c:\program files\vfp9\wwReflection20.dll (my COM client EXE's folder) string info4 = dynParser.GetType().Assembly.CodeBase; // fails parser = (TypeParser)objparser; As you can see the second value is coming from a totally different assembly. Note that this is even though I EXPLICITLY SPECIFIED an assembly path to load the assembly from! Instead .NET decided to load the assembly from the original ApplicationBase folder. Ouch! How I actually tracked this down was a little more tedious: I added a method like this to both the factory and the instance types and then compared notes:public string GetVersionInfo() { return ".NET Version: " + Environment.Version.ToString() + "\r\n" + "wwReflection Assembly: " + typeof(TypeParserFactory).Assembly.CodeBase.Replace("file:///", "").Replace("/", "\\") + "\r\n" + "Assembly Cur Dir: " + Directory.GetCurrentDirectory() + "\r\n" + "ApplicationBase: " + AppDomain.CurrentDomain.SetupInformation.ApplicationBase + "\r\n" + "App Domain: " + AppDomain.CurrentDomain.FriendlyName + "\r\n"; } For the factory I got: .NET Version: 4.0.30319.239wwReflection Assembly: c:\wwapps\wwhelp\bin\wwreflection20.dllAssembly Cur Dir: c:\wwapps\wwhelpApplicationBase: C:\Programs\vfp9\App Domain: wwReflection534cfa1f For the instance type I got: .NET Version: 4.0.30319.239wwReflection Assembly: C:\\Programs\\vfp9\wwreflection20.dllAssembly Cur Dir: c:\\wwapps\\wwhelpApplicationBase: C:\\Programs\\vfp9\App Domain: wwDotNetBridge_56006605 which clearly shows the problem. You can see that both are loading from different appDomains but the each is loading the assembly from a different location. Probably a better solution yet (for ANY kind of assembly loading problem) is to use the .NET Fusion Log Viewer to trace assembly loads.The Fusion viewer will show a load trace for each assembly loaded and where it's looking to find it. Here's what the viewer looks like: The last trace above that I found for the second wwReflection20 load (the one that is wonky) looks like this:*** Assembly Binder Log Entry (1/13/2012 @ 3:06:49 AM) *** The operation was successful. Bind result: hr = 0x0. The operation completed successfully. Assembly manager loaded from: C:\Windows\Microsoft.NET\Framework\V4.0.30319\clr.dll Running under executable c:\programs\vfp9\vfp9.exe --- A detailed error log follows. === Pre-bind state information === LOG: User = Ras\ricks LOG: DisplayName = wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null (Fully-specified) LOG: Appbase = file:///C:/Programs/vfp9/ LOG: Initial PrivatePath = NULL LOG: Dynamic Base = NULL LOG: Cache Base = NULL LOG: AppName = vfp9.exe Calling assembly : (Unknown). === LOG: This bind starts in default load context. LOG: Using application configuration file: C:\Programs\vfp9\vfp9.exe.Config LOG: Using host configuration file: LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\V4.0.30319\config\machine.config. LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind). LOG: Attempting download of new URL file:///C:/Programs/vfp9/wwReflection20.DLL. LOG: Assembly download was successful. Attempting setup of file: C:\Programs\vfp9\wwReflection20.dll LOG: Entering run-from-source setup phase. LOG: Assembly Name is: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null LOG: Binding succeeds. Returns assembly from C:\Programs\vfp9\wwReflection20.dll. LOG: Assembly is loaded in default load context. WRN: The same assembly was loaded into multiple contexts of an application domain: WRN: Context: Default | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: Context: LoadFrom | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: This might lead to runtime failures. WRN: It is recommended to inspect your application on whether this is intentional or not. WRN: See whitepaper http://go.microsoft.com/fwlink/?LinkId=109270 for more information and common solutions to this issue. Notice that the fusion log clearly shows that the .NET loader makes no attempt to even load the assembly from the path I explicitly specified. Remember your Assembly Locations As mentioned earlier all failures I've seen like this ultimately resulted from different versions of the same type being available in the two AppDomains. At first sight that seems ridiculous - how could the types be different and why would you have multiple assemblies - but there are actually a number of scenarios where it's quite possible to have multiple copies of the same assembly floating around in multiple places. If you're hosting different environments (like hosting the Razor Engine, or ASP.NET Runtime for example) it's common to create a private BIN folder and it's important to make sure that there's no overlap of assemblies. In my case of Html Help Builder the problem started because I'm using COM interop to access the .NET assembly and the above code. COM Interop has very specific requirements on where assemblies can be found and because I was mucking around with the loader code today, I ended up moving assemblies around to a new location for explicit loading. The explicit load works in the main AppDomain, but failed in the remote domain as I showed. The solution here was simple enough: Delete the extraneous assembly which was left around by accident. Not a common problem, but one that when it bites is pretty nasty to figure out because it seems so unlikely that types wouldn't match. I know I've run into this a few times and writing this down hopefully will make me remember in the future rather than poking around again for an hour trying to debug the issue as I did today. Hopefully it'll save some of you some time as well in the future.© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  COM   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Changing the connection factory JNDI dynamically in Ftp Adapter

    - by [email protected]
    Consider a usecase where you need to send the same file over to five different ftp servers. The first thought that might come to mind is to create five FtpAdapter references one for each connection-factory location. However, this is not the most optimal approach and this is exactly where "Dynamic Partner Links" come into play in 11g.    If you're running the adapter in managed mode, it would require you to configure the connection factory JNDI in the appserver console for the FtpAdapter. In the sample below, I have mapped the connection-factory JNDI location "eis/Ftp/FtpAdapter" with the ftp server running on localhost.           After you've configured the connection factory on your appserver, you will need to refer to the connection-factory JNDI in the jca artifact of your SCA process. In the example below, I've instructed the FTPOut reference to use the ftp server corresponding to "eis/Ftp/FtpAdapter".     The good news is that you can change this connection-factory location dynamically using jca header properties in both BPEL as well as Mediator service engines. In order to do so, the business scenario involving BPEL or Mediator would be required to use a reserved jca header property "jca.jndi" as shown below.     Similarly, for mediator, the mplan would look as shown below.       Things to remember while using dynamic partner links: 1) The connection factories must be pre-configured on the SOA server. In our BPEL example above, both "eis/Ftp/FtpAdater1" and "eis/Ftp/FtpAdater2" must be configured in the weblogic deployment descriptor for the FtpAdapter prior to deploying the scenario. 2) Dynamic Partner Links are applicable to outbound invocations only.    

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  • SharePoint Unit Testing and Load Testing Finally?

    - by Kit Ong
    It has always been a real pain to incorporate extensive SharePoint Unit Testing and Load Testing in a project, could Visual Studio 2012 finally make this easier? It certaining looks like it, here's a brief overview on SharePoint support in Visual Studio 2012. Load testing – We now support load testing for SharePoint out of the box. This is more involved than you might imagine due to how dynamic SharePoint is. You can’t just record a script and play it back – it won’t work because SharePoint generates and expects dynamic data (like GUIDs). We’ve built the extensions to our load testing solution to parse the dynamic SharePoint data and include it appropriately in subsequent requests. So now you can record a script and play it back and we will dynamically adjust it to match what SharePoint expects.Unit testing – One of the big problems with unit testing SharePoint is that most code requires SharePoint to be running and trying to run tests against a live SharePoint instance is a pain. So we’ve built a SharePoint “emulator” using our new VS 2012 Fakes & Stubs capability. This will make unit testing of SharePoint components WAY easier.Read more in the link belowhttp://blogs.msdn.com/b/bharry/archive/2012/09/12/visual-studio-update-this-fall.aspx

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  • Inside the DLR – Invoking methods

    - by Simon Cooper
    So, we’ve looked at how a dynamic call is represented in a compiled assembly, and how the dynamic lookup is performed at runtime. The last piece of the puzzle is how the resolved method gets invoked, and that is the subject of this post. Invoking methods As discussed in my previous posts, doing a full lookup and bind at runtime each and every single time the callsite gets invoked would be far too slow to be usable. The results obtained from the callsite binder must to be cached, along with a series of conditions to determine whether the cached result can be reused. So, firstly, how are the conditions represented? These conditions can be anything; they are determined entirely by the semantics of the language the binder is representing. The binder has to be able to return arbitary code that is then executed to determine whether the conditions apply or not. Fortunately, .NET 4 has a neat way of representing arbitary code that can be easily combined with other code – expression trees. All the callsite binder has to return is an expression (called a ‘restriction’) that evaluates to a boolean, returning true when the restriction passes (indicating the corresponding method invocation can be used) and false when it does’t. If the bind result is also represented in an expression tree, these can be combined easily like so: if ([restriction is true]) { [invoke cached method] } Take my example from my previous post: public class ClassA { public static void TestDynamic() { CallDynamic(new ClassA(), 10); CallDynamic(new ClassA(), "foo"); } public static void CallDynamic(dynamic d, object o) { d.Method(o); } public void Method(int i) {} public void Method(string s) {} } When the Method(int) method is first bound, along with an expression representing the result of the bind lookup, the C# binder will return the restrictions under which that bind can be reused. In this case, it can be reused if the types of the parameters are the same: if (thisArg.GetType() == typeof(ClassA) && arg1.GetType() == typeof(int)) { thisClassA.Method(i); } Caching callsite results So, now, it’s up to the callsite to link these expressions returned from the binder together in such a way that it can determine which one from the many it has cached it should use. This caching logic is all located in the System.Dynamic.UpdateDelegates class. It’ll help if you’ve got this type open in a decompiler to have a look yourself. For each callsite, there are 3 layers of caching involved: The last method invoked on the callsite. All methods that have ever been invoked on the callsite. All methods that have ever been invoked on any callsite of the same type. We’ll cover each of these layers in order Level 1 cache: the last method called on the callsite When a CallSite<T> object is first instantiated, the Target delegate field (containing the delegate that is called when the callsite is invoked) is set to one of the UpdateAndExecute generic methods in UpdateDelegates, corresponding to the number of parameters to the callsite, and the existance of any return value. These methods contain most of the caching, invoke, and binding logic for the callsite. The first time this method is invoked, the UpdateAndExecute method finds there aren’t any entries in the caches to reuse, and invokes the binder to resolve a new method. Once the callsite has the result from the binder, along with any restrictions, it stitches some extra expressions in, and replaces the Target field in the callsite with a compiled expression tree similar to this (in this example I’m assuming there’s no return value): if ([restriction is true]) { [invoke cached method] return; } if (callSite._match) { _match = false; return; } else { UpdateAndExecute(callSite, arg0, arg1, ...); } Woah. What’s going on here? Well, this resulting expression tree is actually the first level of caching. The Target field in the callsite, which contains the delegate to call when the callsite is invoked, is set to the above code compiled from the expression tree into IL, and then into native code by the JIT. This code checks whether the restrictions of the last method that was invoked on the callsite (the ‘primary’ method) match, and if so, executes that method straight away. This means that, the next time the callsite is invoked, the first code that executes is the restriction check, executing as native code! This makes this restriction check on the primary cached delegate very fast. But what if the restrictions don’t match? In that case, the second part of the stitched expression tree is executed. What this section should be doing is calling back into the UpdateAndExecute method again to resolve a new method. But it’s slightly more complicated than that. To understand why, we need to understand the second and third level caches. Level 2 cache: all methods that have ever been invoked on the callsite When a binder has returned the result of a lookup, as well as updating the Target field with a compiled expression tree, stitched together as above, the callsite puts the same compiled expression tree in an internal list of delegates, called the rules list. This list acts as the level 2 cache. Why use the same delegate? Stitching together expression trees is an expensive operation. You don’t want to do it every time the callsite is invoked. Ideally, you would create one expression tree from the binder’s result, compile it, and then use the resulting delegate everywhere in the callsite. But, if the same delegate is used to invoke the callsite in the first place, and in the caches, that means each delegate needs two modes of operation. An ‘invoke’ mode, for when the delegate is set as the value of the Target field, and a ‘match’ mode, used when UpdateAndExecute is searching for a method in the callsite’s cache. Only in the invoke mode would the delegate call back into UpdateAndExecute. In match mode, it would simply return without doing anything. This mode is controlled by the _match field in CallSite<T>. The first time the callsite is invoked, _match is false, and so the Target delegate is called in invoke mode. Then, if the initial restriction check fails, the Target delegate calls back into UpdateAndExecute. This method sets _match to true, then calls all the cached delegates in the rules list in match mode to try and find one that passes its restrictions, and invokes it. However, there needs to be some way for each cached delegate to inform UpdateAndExecute whether it passed its restrictions or not. To do this, as you can see above, it simply re-uses _match, and sets it to false if it did not pass the restrictions. This allows the code within each UpdateAndExecute method to check for cache matches like so: foreach (T cachedDelegate in Rules) { callSite._match = true; cachedDelegate(); // sets _match to false if restrictions do not pass if (callSite._match) { // passed restrictions, and the cached method was invoked // set this delegate as the primary target to invoke next time callSite.Target = cachedDelegate; return; } // no luck, try the next one... } Level 3 cache: all methods that have ever been invoked on any callsite with the same signature The reason for this cache should be clear – if a method has been invoked through a callsite in one place, then it is likely to be invoked on other callsites in the codebase with the same signature. Rather than living in the callsite, the ‘global’ cache for callsite delegates lives in the CallSiteBinder class, in the Cache field. This is a dictionary, typed on the callsite delegate signature, providing a RuleCache<T> instance for each delegate signature. This is accessed in the same way as the level 2 callsite cache, by the UpdateAndExecute methods. When a method is matched in the global cache, it is copied into the callsite and Target cache before being executed. Putting it all together So, how does this all fit together? Like so (I’ve omitted some implementation & performance details): That, in essence, is how the DLR performs its dynamic calls nearly as fast as statically compiled IL code. Extensive use of expression trees, compiled to IL and then into native code. Multiple levels of caching, the first of which executes immediately when the dynamic callsite is invoked. And a clever re-use of compiled expression trees that can be used in completely different contexts without being recompiled. All in all, a very fast and very clever reflection caching mechanism.

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  • Converting a bounded knapsack problem to 0/1 knapsack problem

    - by Ants
    I ran across a problem where goal was to use dynamic programming (instead of other approaches). There is a distance to be spanned, and a set of cables of different lengths. What is the minimum number of cables needed to span the distance exactly? To me this looked like a knapsack problem, but since there could be multiples of a particular length, it was a bounded knapsack problem, rather than a 0/1 knapsack problem. (Treat the value of each item to be its weight.) Taking the naive approach (and not caring about the expansion of the search space), the method I used to convert the bounded knapsack problem into a 0/1 knapsack problem, was simply break up the multiples into singles and apply the well-known dynamic programming algorithm. Unfortunately, this leads to sub-optimal results. For example, given cables: 1 x 10ft, 1 x 7ft, 1 x 6ft, 5 x 3ft, 6 x 2ft, 7 x 1ft If the target span is 13ft, the DP algorithm picks 7+6 to span the distance. A greedy algorithm would have picked 10+3, but it's a tie for minimum number of cables. The problem arises, when trying to span 15ft. The DP algorithm ended up picking 6+3+3+3 to get 4 cables, while the greedy algorithm correctly picks 10+3+2 for only 3 cables. Anyway, doing some light scanning of converting bounded to 0/1, it seems like the well-known approach to convert multiple items to { p, 2p, 4p ... }. My question is how does this conversion work if p+2p+4p does not add up to the number of multiple items. For example: I have 5 3ft cables. I can't very well add { 3, 2x3, 4x3 } because 3+2x3+4x3 5x3. Should I add { 3, 4x3 } instead? [I'm currently trying to grok the "Oregon Trail Knapsack Problem" paper, but it currently looks like the approach used there is not dynamic programming.]

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  • Static pages for large photo album

    - by Phil P
    I'm looking for advice on software for managing a largish photo album for a website. 2000+ pictures, one-time drop (probably). I normally use MarginalHack's album, which does what I want: pre-generate thumbnails and HTML for the pictures, so I can serve without needing a dynamic run-time, so there's less attack surface to worry about. However, it doesn't handle pagination or the like, so it's unwieldy for this case. This is a one-time drop for pictures from a wedding, with a shared usercode/password for distribution to the guests; I don't wish to put the pictures in a third-party hosting environment. I don't wish to use PHP, simply because that's another run-time to worry about, I might relent and use something dynamic if it's Python or Perl based (as I can maintain things written in those). I currently have: Apache serving static files, Album-generated, some sub-directories to divide up the content to be a little more manageable. Something like Album but with pagination already handled would be great, but I'm willing to have something a little more dynamic, if it lets people comment or caption and store the extra data in something like an sqlite DB. I'd want something light-weight, not a full-blown CMS with security updates every three months. I don't want to upload pictures of other peoples' children into a third-party free service where I don't know what the revenue model is. (For my site: revenue is none, costs out of pocket). Existing server hosting is *nix, Apache, some WSGI. Client-side I have MacOS. Any advice?

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  • Should I redo an abandoned project with Lightswitch?

    - by Elson
    I had a small project that I was doing on the side. It was basically a couple of forms linked to a DB. Access was out, because it was a specifically meant to be a web application. Being a small project I used ASP.NET Dynamic Data, but, for various reasons, the project ended before deployment. I met the client recently, and he said there was a need for it still. I'm considering restarting the project with Dynamic Data, but I've seen some Lightswitch demos, and was suitably impressed with the BETA. I will wait for RTM if I use it, but is it a good idea to use Lightswitch to replace the Dyanmic Data? The amount of work I put into the Dynamic Data site isn't really an issue. Additional information: It's a system that tracks production in a small factory, broken down by line, machine, section and will generate reports. I would guess that the data structure will remain fairly constant over time, but that the reporting requirements will grow. The other thing is that the factory is part of a larger group, and I'm hopeful that, if this system succeeds, similar work with be forthcoming for other factories.

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  • Generating custom-form documents from base-form plus XML?

    - by KlaymenDK
    Hi all, this is my first stack overflow, and it's a complex one. Sorry. My task is to generate custom documents from a basic template plus some XML without having a custom form design element for each case. Here's the whole picture: We are building a Lotus Notes (client, not web) application for world-wide application access control; the scope is something like 400.000 users being able to request access to any of 1000+ applications. Each application needs its own request form -- different number of approvers, various info required, that sort of thing. We simply can't have a thousand forms in a database (one per application), and anyway their maintenance really needs to be pushed from the developers to the application owners. So instead of custom forms, we'd like to create a generic "template" form that stores a block of basic fields, but then allows application owners to define another block of fields dynamically -- "I want a mandatory plain-text field named 'Name' here, and then a date field named 'Due' here that must be later than today's date, and then ...". I hope this makes sense (if not, think of it as a generic questionnaire application). I pretty much have the structure in place for designing the dynamic fields (form builder GUI - XML-encoded data - pre-rendered DXL for injecting into a form), including mark-up for field types, value options, and rudimentary field validation instructions. My problem is generating a document with this dynamic content injected at the proper location (without needing a custom form design element for each case). Doing the dynamic content via HTML is out. The Notes client web rendering is simply way too poor, and it would be quite a challenge to implement things like field validation instructions, date selectors, and name look-ups. DXL, on the other hand, would allow us to use native Notes fields and code. As a tech demo, I've managed to implement a custom form generator that injects the pre-rendered DXL for the dynamic content into a base form; but as I said, we don't want a ton of custom form design elements. I've tried to implement a way to create a document with the "store form in document" flag set, but once I've created the document from the base form, I can't get DXL access to the stored form design, and so I can't inject my dynamic content. I know this is not something Notes was ever intended to do. Has anyone ever tried something like it (and gotten away with it)? Thanks for reading this far. With a boatload of thanks in advance, Jan Gundtofte-Bruun

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  • Transactional Messaging in the Windows Azure Service Bus

    - by Alan Smith
    Introduction I’m currently working on broadening the content in the Windows Azure Service Bus Developer Guide. One of the features I have been looking at over the past week is the support for transactional messaging. When using the direct programming model and the WCF interface some, but not all, messaging operations can participate in transactions. This allows developers to improve the reliability of messaging systems. There are some limitations in the transactional model, transactions can only include one top level messaging entity (such as a queue or topic, subscriptions are no top level entities), and transactions cannot include other systems, such as databases. As the transaction model is currently not well documented I have had to figure out how things work through experimentation, with some help from the development team to confirm any questions I had. Hopefully I’ve got the content mostly correct, I will update the content in the e-book if I find any errors or improvements that can be made (any feedback would be very welcome). I’ve not had a chance to look into the code for transactions and asynchronous operations, maybe that would make a nice challenge lab for my Windows Azure Service Bus course. Transactional Messaging Messaging entities in the Windows Azure Service Bus provide support for participation in transactions. This allows developers to perform several messaging operations within a transactional scope, and ensure that all the actions are committed or, if there is a failure, none of the actions are committed. There are a number of scenarios where the use of transactions can increase the reliability of messaging systems. Using TransactionScope In .NET the TransactionScope class can be used to perform a series of actions in a transaction. The using declaration is typically used de define the scope of the transaction. Any transactional operations that are contained within the scope can be committed by calling the Complete method. If the Complete method is not called, any transactional methods in the scope will not commit.   // Create a transactional scope. using (TransactionScope scope = new TransactionScope()) {     // Do something.       // Do something else.       // Commit the transaction.     scope.Complete(); }     In order for methods to participate in the transaction, they must provide support for transactional operations. Database and message queue operations typically provide support for transactions. Transactions in Brokered Messaging Transaction support in Service Bus Brokered Messaging allows message operations to be performed within a transactional scope; however there are some limitations around what operations can be performed within the transaction. In the current release, only one top level messaging entity, such as a queue or topic can participate in a transaction, and the transaction cannot include any other transaction resource managers, making transactions spanning a messaging entity and a database not possible. When sending messages, the send operations can participate in a transaction allowing multiple messages to be sent within a transactional scope. This allows for “all or nothing” delivery of a series of messages to a single queue or topic. When receiving messages, messages that are received in the peek-lock receive mode can be completed, deadlettered or deferred within a transactional scope. In the current release the Abandon method will not participate in a transaction. The same restrictions of only one top level messaging entity applies here, so the Complete method can be called transitionally on messages received from the same queue, or messages received from one or more subscriptions in the same topic. Sending Multiple Messages in a Transaction A transactional scope can be used to send multiple messages to a queue or topic. This will ensure that all the messages will be enqueued or, if the transaction fails to commit, no messages will be enqueued.     An example of the code used to send 10 messages to a queue as a single transaction from a console application is shown below.   QueueClient queueClient = messagingFactory.CreateQueueClient(Queue1);   Console.Write("Sending");   // Create a transaction scope. using (TransactionScope scope = new TransactionScope()) {     for (int i = 0; i < 10; i++)     {         // Send a message         BrokeredMessage msg = new BrokeredMessage("Message: " + i);         queueClient.Send(msg);         Console.Write(".");     }     Console.WriteLine("Done!");     Console.WriteLine();       // Should we commit the transaction?     Console.WriteLine("Commit send 10 messages? (yes or no)");     string reply = Console.ReadLine();     if (reply.ToLower().Equals("yes"))     {         // Commit the transaction.         scope.Complete();     } } Console.WriteLine(); messagingFactory.Close();     The transaction scope is used to wrap the sending of 10 messages. Once the messages have been sent the user has the option to either commit the transaction or abandon the transaction. If the user enters “yes”, the Complete method is called on the scope, which will commit the transaction and result in the messages being enqueued. If the user enters anything other than “yes”, the transaction will not commit, and the messages will not be enqueued. Receiving Multiple Messages in a Transaction The receiving of multiple messages is another scenario where the use of transactions can improve reliability. When receiving a group of messages that are related together, maybe in the same message session, it is possible to receive the messages in the peek-lock receive mode, and then complete, defer, or deadletter the messages in one transaction. (In the current version of Service Bus, abandon is not transactional.)   The following code shows how this can be achieved. using (TransactionScope scope = new TransactionScope()) {       while (true)     {         // Receive a message.         BrokeredMessage msg = q1Client.Receive(TimeSpan.FromSeconds(1));         if (msg != null)         {             // Wrote message body and complete message.             string text = msg.GetBody<string>();             Console.WriteLine("Received: " + text);             msg.Complete();         }         else         {             break;         }     }     Console.WriteLine();       // Should we commit?     Console.WriteLine("Commit receive? (yes or no)");     string reply = Console.ReadLine();     if (reply.ToLower().Equals("yes"))     {         // Commit the transaction.         scope.Complete();     }     Console.WriteLine(); }     Note that if there are a large number of messages to be received, there will be a chance that the transaction may time out before it can be committed. It is possible to specify a longer timeout when the transaction is created, but It may be better to receive and commit smaller amounts of messages within the transaction. It is also possible to complete, defer, or deadletter messages received from more than one subscription, as long as all the subscriptions are contained in the same topic. As subscriptions are not top level messaging entities this scenarios will work. The following code shows how this can be achieved. try {     using (TransactionScope scope = new TransactionScope())     {         // Receive one message from each subscription.         BrokeredMessage msg1 = subscriptionClient1.Receive();         BrokeredMessage msg2 = subscriptionClient2.Receive();           // Complete the message receives.         msg1.Complete();         msg2.Complete();           Console.WriteLine("Msg1: " + msg1.GetBody<string>());         Console.WriteLine("Msg2: " + msg2.GetBody<string>());           // Commit the transaction.         scope.Complete();     } } catch (Exception ex) {     Console.WriteLine(ex.Message); }     Unsupported Scenarios The restriction of only one top level messaging entity being able to participate in a transaction makes some useful scenarios unsupported. As the Windows Azure Service Bus is under continuous development and new releases are expected to be frequent it is possible that this restriction may not be present in future releases. The first is the scenario where messages are to be routed to two different systems. The following code attempts to do this.   try {     // Create a transaction scope.     using (TransactionScope scope = new TransactionScope())     {         BrokeredMessage msg1 = new BrokeredMessage("Message1");         BrokeredMessage msg2 = new BrokeredMessage("Message2");           // Send a message to Queue1         Console.WriteLine("Sending Message1");         queue1Client.Send(msg1);           // Send a message to Queue2         Console.WriteLine("Sending Message2");         queue2Client.Send(msg2);           // Commit the transaction.         Console.WriteLine("Committing transaction...");         scope.Complete();     } } catch (Exception ex) {     Console.WriteLine(ex.Message); }     The results of running the code are shown below. When attempting to send a message to the second queue the following exception is thrown: No active Transaction was found for ID '35ad2495-ee8a-4956-bbad-eb4fedf4a96e:1'. The Transaction may have timed out or attempted to span multiple top-level entities such as Queue or Topic. The server Transaction timeout is: 00:01:00..TrackingId:947b8c4b-7754-4044-b91b-4a959c3f9192_3_3,TimeStamp:3/29/2012 7:47:32 AM.   Another scenario where transactional support could be useful is when forwarding messages from one queue to another queue. This would also involve more than one top level messaging entity, and is therefore not supported.   Another scenario that developers may wish to implement is performing transactions across messaging entities and other transactional systems, such as an on-premise database. In the current release this is not supported.   Workarounds for Unsupported Scenarios There are some techniques that developers can use to work around the one top level entity limitation of transactions. When sending two messages to two systems, topics and subscriptions can be used. If the same message is to be sent to two destinations then the subscriptions would have the default subscriptions, and the client would only send one message. If two different messages are to be sent, then filters on the subscriptions can route the messages to the appropriate destination. The client can then send the two messages to the topic in the same transaction.   In scenarios where a message needs to be received and then forwarded to another system within the same transaction topics and subscriptions can also be used. A message can be received from a subscription, and then sent to a topic within the same transaction. As a topic is a top level messaging entity, and a subscription is not, this scenario will work.

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