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• DRY Validation with MVC2

  - by Matthew

  Hi All, I'm trying to figure out how I can define validation rules for my domain objects in one single location within my application but have run in to a snag... Some background: My location has several parts: - Database - DAL - Business Logic Layer - SOAP API Layer - MVC website The MVC website accesses the database via the SOAP API, just as third parties would. We are using server and and client side validation on the MVC website as well as in the SOAP API Layer. To avoid having to manually write client side validation we are implementing strongly typed views in conjunction with the Html.TextBoxFor and Html.ValidationMessageFor HTML helpers, as shown in Step 3 here. We also create custom models for each form where one form takes input for multiple domain objects. This is where the problem begins, the HTML helpers read from the model for the data annotation validation attributes. In most cases our forms deal with multiple domain objects and you can't specify more than one type in the <%@Page ... Inherits="System.Web.Mvc.ViewPage" % page directive. So we are forced to create a custom model class, which would mean duplicating validation attributes from the domain objects on to the model class. I've spent quite some time looking for workarounds to this, such has referencing the same MetadataType from both the domain class and the custom MVC models, but that won't work for several reasons: You can only specify one MetadataType attribute per class, so its a problem if a model references multiple domain objects, each with their own metadata type. The data annotation validation code throws an exception if the model class doesn't contain a property that is specified in the referenced MetadataType which is a problem with the model only deals with a subset of the properties for a given domain object. I've looked at other solutions as well but to no avail. If anyone has any ideas on how to achieve a single source for validation logic that would work across MVC client and server side validation functionality and other locations (such as my SOAP API) I would love to hear it! Thanks in advance, Matthew

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• Entity Framework 4 Code First and the new() Operator

  - by Eric J.

  I have a rather deep hierarchy of objects that I'm trying to persist with Entity Framework 4, POCO, PI (Persistence Ignorance) and Code First. Suddenly things started working pretty well when it dawned on me to not use the new() operator. As originally written, the objects frequently use new() to create child objects. Instead I'm using my take on the Repository Pattern to create all child objects as needed. For example, given: class Adam { List<Child> children; void AddChildGivenInput(string input) { children.Add(new Child(...)); } } class Child { List<GrandChild> grandchildren; void AddGrandChildGivenInput(string input) { grandchildren.Add(new GrandChild(...)); } } class GrandChild { } ("GivenInput" implies some processing not shown here) I define an AdamRepository like: class AdamRepository { Adam Add() { return objectContext.Create<Adam>(); } Child AddChildGivenInput(Adam adam, string input) { return adam.children.Add(new Child(...)); } GrandChild AddGrandchildGivenInput(Child child, string input) { return child.grandchildren.Add(new GrandChild(...)); } } Now, this works well enough. However, I'm no longer "ignorant" of my persistence mechanism as I have abandoned the new() operator. Additionally, I'm at risk of an anemic domain model since so much logic ends up in the repository rather than in the domain objects. After much adieu, a question: Or rather several questions... Is this pattern required to work with EF 4 Code First? Is there a way to retain use of new() and still work with EF 4 / POCO / Code First? Is there another pattern that would leave logic in the domain object and still work with EF 4 / POCO / Code First? Will this restriction be lifted in later versions of Code First support? Sometimes trying to go the POCO / Persistence Ignorance route feels like swimming upstream, other times it feels like swimming up Niagra Falls.

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• Mapping and metadata information could not be found for EntityType Exception

  - by dcompiled

  I am trying out ASP.NET MVC Framework 2 with the Microsoft Entity Framework and when I try and save new records I get this error: Mapping and metadata information could not be found for EntityType 'WebUI.Controllers.PersonViewModel' My Entity Framework container stores records of type Person and my view is strongly typed with class PersonViewModel which derives from Person. Records would save properly until I tried to use the derived view model class. Can anyone explain why the metadata class doesnt work when I derive my view model? I want to be able to use a strongly typed model and also use data annotations (metadata) without resorting to mixing my storage logic (EF classes) and presentation logic (views). // Rest of the Person class is autogenerated by the EF [MetadataType(typeof(Person.Metadata))] public partial class Person { public sealed class Metadata { [DisplayName("First Name")] [Required(ErrorMessage = "Field [First Name] is required")] public object FirstName { get; set; } [DisplayName("Middle Name")] public object MiddleName { get; set; } [DisplayName("Last Name")] [Required(ErrorMessage = "Field [Last Name] is required")] public object LastName { get; set; } } } // From the View (PersonCreate.aspx) <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<WebUI.Controllers.PersonViewModel>" %> // From PersonController.cs public class PersonViewModel : Person { public List<SelectListItem> TitleList { get; set; } } // end class PersonViewModel

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• serializing type definitions?

  - by Dave

  I'm not positive I'm going about this the right way. I've got a suite of applications that have varying types of output (custom defined types). For example, I might have a type called Widget: Class Widget Public name as String End Class Throughout the course of operation, when a user experiences a certain condition, the application will take that output instance of widget that user received, serialize it, and log it to the database noting the name of the type. Now, I have other applications that do something similar, but instead of dealing with Widget, it could be some totally random other type with different attributes, but again I serialize the instance, log it to the db, and note the name of the type. I have maybe a half dozen different types and don't anticipate too many additional ones in the future. After all this is said and done, I have an admin interface that looks through these logs, and has the ability for the user to view the contents of this data thats been logged. The Admin app has a reference to all the types involved, and with some basic switch case logic hinged upon the name of the type, will cast it into their original types, and pass it on to some handlers that have basic display logic to spit the data back out in a readable format (one display handler for each type) NOW... all this is well and good... Until one day, my model changed. The Widget class now has deprecated the name attribute and added on a bunch of other attributes. I will of course get type mismatches in the admin side when I try to reconstitute this data. I was wondering if there was some way, at runtime, i could perhaps reflect through my code and get a snapshot of the type definition at that precise moment, serialize it, and store it along with the data so that I could somehow use this to reconstitute it in the future?

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• Notifying view controller when subview touch events occur.

  - by Nebs

  I have a UIViewController whose view has a custom subview. This custom subview needs to track touch events and report swipe gestures. Currently I put touchesBegan, touchesMoved, touchesEnded and touchesCancelled in the subview class. With some extra logic I am able to get swipe gestures and call my handleRightSwipe and handleLeftSwipe methods. So now when I swipe within the subview it calls its local swipe handling methods. This all works fine. But what I really need is for the handleRightSwipe and handleLeftSwipe methods to be in the view controller. I could leave them in the subview class but then I'd have to bring in all the logic and data as well and that kind of breaks the MVC idea. So my question is is there a clean way to handle this? Essentially I want to keep my touch event methods in the subview so that they only trigger for that specific view. But I also want the view controller to be informed when these touch events (or in this case swipe gestures) occur. Any ideas? Thanks.

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• Why use short-circuit code?

  - by Tim Lytle

  Related Questions: Benefits of using short-circuit evaluation, Why would a language NOT use Short-circuit evaluation?, Can someone explain this line of code please? (Logic & Assignment operators) There are questions about the benefits of a language using short-circuit code, but I'm wondering what are the benefits for a programmer? Is it just that it can make code a little more concise? Or are there performance reasons? I'm not asking about situations where two entities need to be evaluated anyway, for example: if($user->auth() AND $model->valid()){ $model->save(); } To me the reasoning there is clear - since both need to be true, you can skip the more costly model validation if the user can't save the data. This also has a (to me) obvious purpose: if(is_string($userid) AND strlen($userid) > 10){ //do something }; Because it wouldn't be wise to call strlen() with a non-string value. What I'm wondering about is the use of short-circuit code when it doesn't effect any other statements. For example, from the Zend Application default index page: defined('APPLICATION_PATH') || define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); This could have been: if(!defined('APPLICATION_PATH')){ define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); } Or even as a single statement: if(!defined('APPLICATION_PATH')) define('APPLICATION_PATH', realpath(dirname(__FILE__) . '/../application')); So why use the short-circuit code? Just for the 'coolness' factor of using logic operators in place of control structures? To consolidate nested if statements? Because it's faster?

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• Writing files in App_Data causes tempdata to be null

  - by RAMX

  I have a small asp.net MVC 1 web app that can store files and create directories in the App_Data directory. When the write operation succeeds, I add a message to the tempdata and do a redirectToRoute. The problem is that the tempdata is null when the action is executed. If i write the files in a directory outside of the web applications root directory, the tempdata is not null and everything works correctly. Any ideas why writing in the app_data seems to clear the tempdata ? edit: if DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment) writes in the App_Data, TempData will be null in the action being redirected to. if it is a directory out of the web app root it is fine. No exceptions are being thrown. [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(int id, string path, FormCollection form) { ViewData["path"] = path; ViewData["id"] = id; HttpPostedFileBase hpf; string comment = form["FileComment"]; hpf = Request.Files["File"] as HttpPostedFileBase; if (hpf.ContentLength != 0) { DRS.Logic.Repository.Manager.CreateFile(path, hpf, comment); TempData["notification"] = "file was created"; return RedirectToRoute(new { controller = "File", action ="ViewDetails", id = id, path = path + Path.GetFileName(hpf.FileName) }); } else { TempData["notification"] = "No file were selected."; return View(); } }

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• OrientationEventListener not working properly

  - by nixau

  Hi all, I need to handle orientation changes in my Android application. For this purpose I decided to use OrientationEventListener convenience class. But his callback method is given somewhat strange behavior. My application starts in the portrait mode and then eventually switches to the lanscape one. I have some custom code executing in the callback onOrientationChanged method that provides some additional UI handling logic - it has a few calls to findViewById. What is strange is that when switching back from landscape to portrait mode onOrientationChanged callback is called twice, and what's even worse - the second call is dealing with bad Context - findViewById method starts returning null. These calls are made right from the MainThread @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); listener = new OrientationListener(); } @Override protected void onResume() { super.onResume(); // enabling listening listener.enable(); } @Override protected void onPause() { super.onPause(); // disabling listening listener.disable(); } I've replicated the same behavior with a dummy Activity without any logic except for one that deals with orientation hadling. I initiate orientation switch from the Android 2.2 emulator by pressing Ctrl+F11 What could be wrong? Upd: Inner class that implements OrientationEventListener private class OrientationListener extends OrientationEventListener { public OrientationL() { super(getBaseContext()); } @Override public void onOrientationChanged(int orientation) { toString(); } } }

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• How to inject a Session Bean into a Message Driven Bean?

  - by Hank

  Hi guys, I'm reasonably new to JEE, so this might be stupid.. bear with me pls :D I would like to inject a stateless session bean into a message-driven bean. Basically, the MDB gets a JMS message, then uses a session bean to perform the work. The session bean holds the business logic. Here's my Session Bean: @Stateless public class TestBean implements TestBeanRemote { public void doSomething() { // business logic goes here } } The matching interface: @Remote public interface TestBeanRemote { public void doSomething(); } Here's my MDB: @MessageDriven(mappedName = "jms/mvs.TestController", activationConfig = { @ActivationConfigProperty(propertyName = "acknowledgeMode", propertyValue = "Auto-acknowledge"), @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue") }) public class TestController implements MessageListener { @EJB private TestBean testBean; public TestController() { } public void onMessage(Message message) { testBean.doSomething(); } } So far, not rocket science, right? Unfortunately, when deploying this to glassfish v3, and sending a message to the appropriate JMS Queue, I get errors that glassfish is unable to locate the TestBean EJB: java.lang.IllegalStateException: Exception attempting to inject Remote ejb-ref name=mvs.test.TestController/testBean,Remote 3.x interface =mvs.test.TestBean,ejb-link=null,lookup=null,mappedName=,jndi-name=mvs.test.TestBean,refType=Session into class mvs.test.TestController Caused by: com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting to inject Remote ejb-ref name=mvs.test.TestController/testBean,Remote 3.x interface =mvs.test.TestBean,ejb-link=null,lookup=null,mappedName=,jndi-name=mvs.test.TestBean,refType=Session into class mvs.test.TestController Caused by: javax.naming.NamingException: Lookup failed for 'java:comp/env/mvs.test.TestController/testBean' in SerialContext [Root exception is javax.naming.NamingException: Exception resolving Ejb for 'Remote ejb-ref name=mvs.test.TestController/testBean,Remote 3.x interface =mvs.test.TestBean,ejb-link=null,lookup=null,mappedName=,jndi-name=mvs.test.TestBean,refType=Session' . Actual (possibly internal) Remote JNDI name used for lookup is 'mvs.test.TestBean#mvs.test.TestBean' [Root exception is javax.naming.NamingException: Lookup failed for 'mvs.test.TestBean#mvs.test.TestBean' in SerialContext [Root exception is javax.naming.NameNotFoundException: mvs.test.TestBean#mvs.test.TestBean not found]]] So my questions are: - is this the correct way of injecting a session bean into another bean (particularly a message driven bean)? - why is the naming lookup failing? Thanks for all your help! Cheers, Hank

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• VB.Net Custom Object Master-Detail Data Binding

  - by clawson

  Since beginning to use VB.Net some years ago I have become slowly familiar with using the data binding features of .Net, however I often find my self bewildered by it's behavior and instead of discover the correct way it should work I find some dirty work around to suit my needs and continue on. Needless to say my problems continue to arise. I am using Custom Objects as the Data Sources for by controls and often entire forms. I find it frustrating to separate business logic and the graphical interface. (That could be a new question entirely.) So for a lot of objects I generate a form which has the DataBindingSource for the object. When I create each from using the New Constructor I explicitly pass to it the object to which it should be bound, and then set this passed object as the DataSource of the BindingSource. (That's a mouthful!) Now the Master object (say, bound to each form) often contains a List of objects which I like to have displayed in a DataGridView. I (sometimes) create and modify these child objects in their own form (again creating a databind the same way as the master form) but when I add them to the List in the master object the DataGridView won't update with the new items. So my question really has a few layers: How can I easily/efficiently/correctly update this DataGridView with the list of Detail objects when I add them to the list of the Master object. Is this approach to DataBinding good/viable. What's the best way to separate business logic from graphical interface. Thanks for the help!

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• Understanding how rpmbuild works

  - by ereOn

  Hi, For my work, I have to create a documentation on "How-to create a RPM package on Red Hat 5". I'm used to Debian and it's derivative (Ubuntu, and so on) and thus to Debian packages (aka. .deb files). It seems that the RPM logic is quite different from what I know already and I am having some issues understanding the "RPM logic". From what I read, it seems that ones need to be root to create a RPM package. While I understand why root could be required to install a package, I still don't understand why elevated privileges should be needed to just create one. If I try to create a RPM package as a user, changing the buildroot it fails on the %installstep because I don't have permission to write files into /usr/bin. Fair enough but... why does he want to copy my files into /usr/bin at this step ?! I just want to create the package, not install it ! I'm sure I'm missing something here. Is there anyone who could give me at least a basic understanding of how rpmbuild works and why ? Thank you very much !

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• What's are the best readings to start using WPF instead of WinForms?

  - by Ivan

  Keeping in mind what CannibalSmith once said - "All the answers are saying "WPF is different". That's a huge understatement. You not only have to learn lots of new stuff - you must forget everything you've learned from Forms. It's a completely new way of doing UI." .. and having many years of experience with visual Windows desktop applications development (VB6, Borland C++ Builder VCL, WinForms) (which is hard to forget), how do I quickly move to developing to say well-formed WPF applications with Visual Studio? I don't need boozy-woozy graphics to give my app look and feel of a Hollywood blockbuster or a million dollar pyjamas. I always loved tidiness of standard Windows common controls and UI design guidelines, end even more I enjoyed them under Vista Glass Aero Graphite sauce. I am perfectly satisfied with WinForms but I want to my applications to be built of the most efficient and up-to-date standard technologies and architectured according to the most efficient and flexible patterns of today and tomorrow, leveraging interface-based integration and functionality reuse and to take all advantages of modern hardware and APIs to maximize performance, usability, reliability, maintainability, extensibility, etc. I very much like the idea of separating view, logic and data, letting a view to take all advantages of the platform (may it run as a web browser applet on a thin client or as a desktop application on a PC with a latest GPU), letting logic be reused, parallelized and seamlessly evolve, storing data in a well structured format in a right place. But... while moving from VB6 to Borland C++ Builder was very easy (no books/tutorials needed to turn it on and start working) (assuming I already knew C++), moving from BCB to WinForms was the same seamless, it does not seem any obvious to me how to do with WPF. So how do I best convert myself from a WinForms developer into a right-way thinking and doing WPF developer?

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• Custom model validation of dependent properties using Data Annotations

  - by Darin Dimitrov

  Since now I've used the excellent FluentValidation library to validate my model classes. In web applications I use it in conjunction with the jquery.validate plugin to perform client side validation as well. One drawback is that much of the validation logic is repeated on the client side and is no longer centralized at a single place. For this reason I'm looking for an alternative. There are many examples out there showing the usage of data annotations to perform model validation. It looks very promising. One thing I couldn't find out is how to validate a property that depends on another property value. Let's take for example the following model: public class Event { [Required] public DateTime? StartDate { get; set; } [Required] public DateTime? EndDate { get; set; } } I would like to ensure that EndDate is greater than StartDate. I could write a custom validation attribute extending ValidationAttribute in order to perform custom validation logic. Unfortunately I couldn't find a way to obtain the model instance: public class CustomValidationAttribute : ValidationAttribute { public override bool IsValid(object value) { // value represents the property value on which this attribute is applied // but how to obtain the object instance to which this property belongs? return true; } } I found that the CustomValidationAttribute seems to do the job because it has this ValidationContext property that contains the object instance being validated. Unfortunately this attribute has been added only in .NET 4.0. So my question is: can I achieve the same functionality in .NET 3.5 SP1? UPDATE: It seems that FluentValidation already supports clientside validation and metadata in ASP.NET MVC 2. Still it would be good to know though if data annotations could be used to validate dependent properties.

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• Where should 'CreateMap' statements go?

  - by jonathanconway

  I frequently use AutoMapper to map Model (Domain) objects to ViewModel objects, which are then consumed by my Views, in a Model/View/View-Model pattern. This involves many 'Mapper.CreateMap' statements, which all must be executed, but must only be executed once in the lifecycle of the application. Technically, then, I should keep them all in a static method somewhere, which gets called from my Application_Start() method (this is an ASP.NET MVC application). However, it seems wrong to group a lot of different mapping concerns together in one central location. Especially when mapping code gets complex and involves formatting and other logic. Is there a better way to organize the mapping code so that it's kept close to the ViewModel that it concerns? (I came up with one idea - having a 'CreateMappings' method on each ViewModel, and in the BaseViewModel, calling this method on instantiation. However, since the method should only be called once in the application lifecycle, it needs some additional logic to cache a list of ViewModel types for which the CreateMappings method has been called, and then only call it when necessary, for ViewModels that aren't in that list.)

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• .NET Membership with Repository Pattern

  - by Zac

  My team is in the process of designing a domain model which will hide various different data sources behind a unified repository abstraction. One of the main drivers for this approach is the very high probability that these data sources will undergo significant change in the near future and we don't want to be re-writing business logic when this happens. One data source will be our membership database which was originally implemented using the default ASP.Net Membership Provider. The membership provider is tied to the System.Web.Security namespace but we have a design guideline requiring that our domain model layer is not dependent upon System.Web (or any other implementation/environment dependency) as it will be consumed in different environments - nor do we want our websites directly communicating with databases. I am considering what would be a good approach to reconciling the MembershipProvider approach with our abstracted n-tier architecture. My initial feeling is that we could create a "DomainMembershipProvider" which interacts with the domain model and then implement objects in the model which deal with the repository and handle validation/business logic. The repository would then implement data access using our (as-yet undecided) ORM/data access tool. Are there are any glaring holes in this approach - I haven't worked closely with the MembershipProvider class so may well be missing something. Alternatively, is there an approach that you think will better serve the requirements I described above? Thanks in advance for your thoughts and advice. Regards, Zac

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• DDD and Client/Server apps

  - by Christophe Herreman

  I was wondering if any of you had successfully implemented DDD in a Client/Server app and would like to share some experiences. We are currently working on a smart client in Flex and a backend in Java. On the server we have a service layer exposed to the client that offers CRUD operations amongst some other service methods. I understand that in DDD these services should be repositories and services should be used to handle use cases that do not fit inside a repository. Right now, we mimic these services on the client behind an interface and inject implementations (Webservices, RMI, etc) via an IoC container. So some questions arise: should the server expose repositories to the client or do we need to have some sort of a facade (that is able to handle security for instance) should the client implement repositories (and DDD in general?) knowing that in the client, most of the logic is view related and real business logic lives on the server. All communication with the server happens asynchronously and we have a single threaded programming model on the client. how about mapping client to server objects and vice versa? We tried DTO's but reverted back to exposing the state of our objects and mapping directly to them. I know this is considered bad practice, but it saves us an incredible amount of time) In general I think a new generation of applications is coming with the growth of Flex, Silverlight, JavaFX and I'm curious how DDD fits into this.

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• ColdFusion 8: Database Connection Reset Error

  - by Gavin

  I have been getting these intermittent ColdFusion Database connection reset errors and was wondering if anyone had experience with this and had a particular solution that worked? Here is the error: Error Executing Database Query.[Macromedia][SQLServer JDBC Driver]A problem occurred when attempting to contact the server (Server returned: Connection reset). Please ensure that the server parameters passed to the driver are correct and that the server is running. Also ensure that the maximum number of connections have not been exceeded for this server. This doesn't happen with any particular query, the code breaks in different queries every time, returning a SQLState error 08s01. These query's logic are fine, no logic errors etc. I checked the network logs and there were no database server connection refusals at the time of the error. Once the first error occurs, it keeps happening for no more than a minute or so at random times of the day, every few days. I've googled this thing and so far anyone that has had this issue was only on CF6 or 7, which the fixes coldFusion put out are only for CF6 or 7. Server configuration wise: The ColdFusion server is version 8 The database server is SQL Server 2005 Standard The database connections allowed setting is set to unlimited on both SQL Server and ColdFusion Any help would be greatly appreciated, Thanks!

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• SQLite on iPhone - Techniques for tracking down multithreading-related bugs

  - by Jasarien

  Hey guys, I'm working with an Objective-C wrapper around SQLite that I didn't write, and documentation is sparse... It's not FMDB. The people writing this wrapper weren't aware of FMDB when writing this code. It seems that the code is suffering from a bug where database connections are being accessed from multiple threads -- which according to the SQLite documentation won't work if the if SQLite is compiled with SQLITE_THREADSAFE 2. I have tested the libsqlite3.dylib provided as part of the iPhone SDK and seen that it is compiled in this manner, using the sqlite_threadsafe() routine. Using the provided sqlite library, the code regularly hits SQLITE_BUSY and SQLITE_LOCKED return codes when performing routines. To combat this, I added some code to wait a couple of milliseconds and try again, with a maximum retry count of 50. The code didn't contain any retry logic prior to this. Now when a sqlite call returns SQLITE_BUSY or SQLITE_LOCKED, the retry loop is invoked and the retry returns SQLITE_MISUSE. Not good. Grasping at straws, I replaced the provided sqlite library with a version compiled by myself setting SQLITE_THREADSAFE to 1 - which according to the documentation means sqlite is safe to be used in a multithreaded environment, effectively serialising all of the operations. It incurs a performance hit, that which I haven't measured, but it ridded the app of the SQLITE_MISUSE happening and seemed to not need the retry logic as it never hit a busy or locked state. What I would rather do is fix the problem of accessing a single db connection from multiple threads, but I can't for the life of me find where it's occurring. So if anyone has any tips on locating multithreaded bugs I would be extremely appreciative. Thanks in advance.

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• What are the most interesting equivalences arising from the Curry-Howard Isomorphism?

  - by Tom

  I came upon the Curry-Howard Isomorphism relatively late in my programming life, and perhaps this contributes to my being utterly fascinated by it. It implies that for every programming concept there exists a precise analogue in formal logic, and vice versa. Here's an "obvious" list of such analogies, off the top of my head: program/definition | proof type/declaration | proposition inhabited type | theorem function | implication function argument | hypothesis/antecedent function result | conclusion/consequent function application | modus ponens recursion | induction identity function | tautology non-terminating function | absurdity tuple | conjunction (and) disjoint union | exclusive disjunction (xor) parametric polymorphism | universal quantification So, to my question: what are some of the more interesting/obscure implications of this isomorphism? I'm no logician so I'm sure I've only scratched the surface with this list. For example, here are some programming notions for which I'm unaware of pithy names in logic: currying | "((a & b) => c) iff (a => (b => c))" scope | "known theory + hypotheses" And here are some logical concepts which I haven't quite pinned down in programming terms: primitive type? | axiom set of valid programs? | theory ? | disjunction (or)

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• ASP.MVC 2 RTM + ModelState Error at Id property

  - by Zote

  I have this classes: public class GroupMetadata { [HiddenInput(DisplayValue = false)] public int Id { get; set; } [Required] public string Name { get; set; } } [MetadataType(typeof(GrupoMetadata))] public partial class Group { public virtual int Id { get; set; } public virtual string Name { get; set; } } And this action: [HttpPost] public ActionResult Edit(Group group) { if (ModelState.IsValid) { // Logic to save return RedirectToAction("Index"); } return View(group); } That's my view: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<Group>" %> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <% using (Html.BeginForm()) {%> <fieldset> <%= Html.EditorForModel() %> <p> <input type="submit" value="Save" /> </p> </fieldset> <% } %> <div> <%=Html.ActionLink("Back", "Index") %> </div> </asp:Content> But ModelState is always invalid! As I can see, for MVC validation 0 is invalid, but for me is valid. How can I fix it since, I didn't put any kind of validation in Id property? UPDATE: I don't know how or why, but renaming Id, in my case to PK, solves this problem. Do you know if this an issue in my logic/configuration or is an bug or expected behavior? Thank you

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• Custom model validation of dependent properties using Data Annotations

  - by Darin Dimitrov

  Since now I've used the excellent FluentValidation library to validate my model classes. In web applications I use it in conjunction with the jquery.validate plugin to perform client side validation as well. One drawback is that much of the validation logic is repeated on the client side and is no longer centralized at a single place. For this reason I'm looking for an alternative. There are many examples out there showing the usage of data annotations to perform model validation. It looks very promising. One thing I couldn't find out is how to validate a property that depends on another property value. Let's take for example the following model: public class Event { [Required] public DateTime? StartDate { get; set; } [Required] public DateTime? EndDate { get; set; } } I would like to ensure that EndDate is greater than StartDate. I could write a custom validation attribute extending ValidationAttribute in order to perform custom validation logic. Unfortunately I couldn't find a way to obtain the model instance: public class CustomValidationAttribute : ValidationAttribute { public override bool IsValid(object value) { // value represents the property value on which this attribute is applied // but how to obtain the object instance to which this property belongs? return true; } } I found that the CustomValidationAttribute seems to do the job because it has this ValidationContext property that contains the object instance being validated. Unfortunately this attribute has been added only in .NET 4.0. So my question is: can I achieve the same functionality in .NET 3.5 SP1? UPDATE: It seems that FluentValidation already supports clientside validation and metadata in ASP.NET MVC 2. Still it would be good to know though if data annotations could be used to validate dependent properties.

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• Terminal / Panel PC - Single Server Solution: Client/Server or RDP?

  - by StillLearning

  Hi, Our current setup involves a touch screen panel pc with embedded windows, that is connected via network to a server / dedicated pc, within the same physical location. Each of our 'units' has this hardware setup. For a quick resolution we deploy our application to the dedicated pc, and have the panel pc remote desktop to an account which then activates the application. This works but seems a little clunky / rough approach. We did this because the panel pc is rather limited. Now that we have more time, I was wondering if I should separate the application into a gui / application. Deploy the gui logic on the panel pc, and the business/database logic on the dedicated pc. The app is in Java so I was wondering what technology would be best? I was thinking of using RMI, but its not really a client/server app, as there is only one client. Should I stick with RMI, or use Sockets or something else? It will be easy to implement as the application is old, and manually wraps and unwraps data which passes through one class / method call to remote services. All I would have to do is 'RMI' this one method call, and the app will do its own stuff. Cheers.

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• How do I implement repository pattern and unit of work when dealing with multiple data stores?

  - by Jason

  I have a unique situation where I am building a DDD based system that needs to access both Active Directory and a SQL database as persistence. Initially this wasnt a problem because our design was setup where we had a unit of work that looked like this: public interface IUnitOfWork { void BeginTransaction() void Commit() } and our repositories looked like this: public interface IRepository<T> { T GetByID() void Save(T entity) void Delete(T entity) } In this setup our load and save would handle the mapping between both data stores because we wrote it ourselves. The unit of work would handle transactions and would contain the Linq To SQL data context that the repositories would use for persistence. The active directory part was handled by a domain service implemented in infrastructure and consumed by the repositories in each Save() method. Save() was responsible with interacting with the data context to do all the database operations. Now we are trying to adapt it to entity framework and take advantage of POCO. Ideally we would not need the Save() method because the domain objects are being tracked by the object context and we would just need to add a Save() method on the unit of work to have the object context save the changes, and a way to register new objects with the context. The new proposed design looks more like this: public interface IUnitOfWork { void BeginTransaction() void Save() void Commit() } public interface IRepository<T> { T GetByID() void Add(T entity) void Delete(T entity) } This solves the data access problem with entity framework, but does not solve the problem with our active directory integration. Before, it was in the Save() method on the repository, but now it has no home. The unit of work knows nothing other than the entity framework data context. Where should this logic go? I argue this design only works if you only have one data store using entity framework. Any ideas how to best approach this issue? Where should I put this logic?

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• NMock2.0 - how to stub a non interface call?

  - by dferraro

  Hello, I have a class API which has full code coverage and uses DI to mock out all the logic in the main class function (Job.Run) which does all the work. I found a bug in production where we werent doing some validation on one of the data input fields. So, I added a stub function called ValidateFoo()... Wrote a unit test against this function to Expect a JobFailedException, ran the test - it failed obviously because that function was empty. I added the validation logic, and now the test passes. Great, now we know the validation works. Problem is - how do I write the test to make sure that ValidateFoo() is actually called inside Job.Run()? ValidateFoo() is a private method of the Job class - so it's not an interface... Is there anyway to do this with NMock2.0? I know TypeMock supports fakes of non interface types. But changing mock libs right now is not an option. At this point if NMock can't support it, I will simply just add the ValidateFoo() call to the Run() method and test things manually - which obviously I'd prefer not to do considering my Job.Run() method has 100% coverage right now. Any Advice? Thanks very much it is appreciated. EDIT: the other option I have in mind is to just create an integration test for my Job.Run functionality (injecting to it true implementations of the composite objects instead of mocks). I will give it a bad input value for that field and then validate that the job failed. This works and covers my test - but it's not really a unit test but instead an integration test that tests one unit of functionality.... hmm.. EDIT2: IS there any way to do tihs? Anyone have ideas? Maybe TypeMock - or a better design?

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• Data Access Layer, Best Practices

  - by labratmatt

  I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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