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  • FormMethod.Get and query string parameters

    - by parminder
    Hi Experts, I am working on a website in asp.net mvc. I have to show a view where user put some search values like tags and titles to search. I want to use the same Index method for that. I have make my form to use formMethod.Get to send the parameters as querystring. so here is the method [HttpGet] public ActionResult Index(string title, string tags, int? page) { if (string.IsNullOrEmpty(title) return View(null); var list = GetSomeData(); return View(list); } here is my view <div id="searchBox"> <% using (Html.BeginForm(null, null, FormMethod.Get)) { %> <table> <tr> <td> <input type="hidden" id="isPosted" name="isPosted" value="1" /> I am looking for <%=Html.TextBox("Title")%> Tags: <%=Html.TextBox("Tags")%> <input id="search" type="submit" value="Search" /> </td> </tr> </table> <% } %> So when the user first visit the page, he will see only two text boxs and a button. but when he types something in the title and tags and click the search button i will load the view with some data. Now the problem is when i type something in title and tags box and click search, they are received in the method, but are not visible in the url. Is there anything i m doing wrong. help will be appreciated. Regards Parminder

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  • What are some programming techniques for converting SD images to HD images

    - by Dr Dork
    I'm taking programming class and instructor loves to work with images so most of our assignments involve manipulating raw RGB image data. One of our assignments is to implement a standard image converter that converts SD images to HD images and vice versa. I always take advantage of these types of assignments to go a little beyond what we were asked to do, so I added a basic anti-aliasing process that uses the average pixel color of the 3x3 surrounding pixels to improve the converted image. While it helps a bit, the resulting image still doesn't look good, which is ok because it's not expected to for the assignment. I've learned that converting an SD to HD images has shown to be much harder than down sampling to SD from HD just because SD to HD effectively involves increasing resolution when it is not there. Obviously, it is hard to create pixels from nothing, but I'd like enhance my anti-aliasing to something that provides better results when upscaling an image. Most of the techniques I find and read on the internet are far beyond my level of image processing and programming. Can anybody suggest any better methods or processes to create good HD content from SD content that may be within my programming skill level? I know that's a difficult thing to gauge since you don't know me, but perhaps knowing that I can write c++ code to read in raw RGB data and upscale/downscale it with simple average-anti-aliasing will give you an idea. Thanks in advance for all your help!

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  • How to customize RESTful Routes in Rails (basics)

    - by viatropos
    I have read through the Rails docs for Routing, Restful Resources, and the UrlHelper, and still don't understand best practices for creating complex/nested routes. The example I'm working on now is for events, which has_many rsvps. So a user's looking through a list of events, and clicks register, and goes through a registration process, etc. I want the urls to look like this: /events /events/123 # possible without title, like SO /events/123/my-event-title # canonical version /events/my-category/123/my-event-title # also possible like this /events/123/my-event-title/registration/new ... and all the restful nested resouces. Question is, how do I accomplish this with the minimal amount of code? Here's what I currently have: map.resources :events do |event| event.resources :rsvps, :as => "registration" end That gets me this: /events/123/registration What's the best way to accomplish the other 2 routes? /events/123/my-event-title # canonical version /events/my-category/123/my-event-title # also possible like this Where my-category is just an array of 10 possible types the event can be. I've modified Event#to_param to return "#{self.id.to_s}-#{self.title.parameterize}", but I'd prefer to have /id/title with the whole canonical-ness

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  • Best Practice - Removing item from generic collection in C#

    - by Matt Davis
    I'm using C# in Visual Studio 2008 with .NET 3.5. I have a generic dictionary that maps types of events to a generic list of subscribers. A subscriber can be subscribed to more than one event. private static Dictionary<EventType, List<ISubscriber>> _subscriptions; To remove a subscriber from the subscription list, I can use either of these two options. Option 1: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { if (_subscriptions[event].Contains(subscriber)) { _subscriptions[event].Remove(subscriber); } } Option 2: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { _subscriptions[event].Remove(subscriber); } I have two questions. First, notice that Option 1 checks for existence before removing the item, while Option 2 uses a brute force removal since Remove() does not throw an exception. Of these two, which is the preferred, "best-practice" way to do this? Second, is there another, "cleaner," more elegant way to do this, perhaps with a lambda expression or using a LINQ extension? I'm still getting acclimated to these two features. Thanks. EDIT Just to clarify, I realize that the choice between Options 1 and 2 is a choice of speed (Option 2) versus maintainability (Option 1). In this particular case, I'm not necessarily trying to optimize the code, although that is certainly a worthy consideration. What I'm trying to understand is if there is a generally well-established practice for doing this. If not, which option would you use in your own code?

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  • Saving "heavy" figure to PDF in MATLAB - rendering problem

    - by yuk
    I generate a figure in MATLAB with lot amount of points (100000+) and want to save it into a PDF file. With zbuffer or painters renderer I've got very large and slowly opened file (over 4 Mb) - all points are in vector format. Using OpenGL renderer rasterize the figure in PDF, ok for the plot, but not good for text labels. The file size is about 150 Kb. Try this simplified code, for example: x=linspace(1,10,100000); y=sin(x)+randn(size(x)); plot(x,y,'.') set(gcf,'Renderer','zbuffer') print -dpdf -r300 testpdf_zb set(gcf,'Renderer','painters') print -dpdf -r300 testpdf_pa set(gcf,'Renderer','opengl') print -dpdf -r300 testpdf_op The actual figure is much more complex with several axes and different types of plots. Is there a way to rasterize the figure, but keep text labels as vectors? Another problem with OpenGL is that is does not work in terminal mode (-nosplash -nodesktop) under Mac OSX. Looks like OpenGL is not supported. I have to use terminal mode for automation. The MATLAB version I run is 2007b. Mac OSX server 10.4.

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  • Using libcurl to create a valid POST

    - by Haraldo
    static int get( const char * cURL, const char * cParam ) { CURL *handle; CURLcode result; std::string buffer; char errorBuffer[CURL_ERROR_SIZE]; //struct curl_slist *headers = NULL; //headers = curl_slist_append(headers, "Content-Type: Multipart/Related"); //headers = curl_slist_append(headers, "type: text/xml"); // Create our curl handle handle = curl_easy_init(); if( handle ) { curl_easy_setopt(handle, CURLOPT_ERRORBUFFER, errorBuffer); //curl_easy_setopt(handle, CURLOPT_HEADER, 0); //curl_easy_setopt(handle, CURLOPT_HTTPHEADER, headers); curl_easy_setopt(handle, CURLOPT_POST, 1); curl_easy_setopt(handle, CURLOPT_POSTFIELDS, cParam); curl_easy_setopt(handle, CURLOPT_POSTFIELDSIZE, strlen(cParam)); curl_easy_setopt(handle, CURLOPT_FOLLOWLOCATION, 1); curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, Request::writer); curl_easy_setopt(handle, CURLOPT_WRITEDATA, &buffer); curl_easy_setopt(handle, CURLOPT_USERAGENT, "libcurl-agent/1.0"); curl_easy_setopt(handle, CURLOPT_URL, cURL); result = curl_easy_perform(handle); curl_easy_cleanup(handle); } if( result == CURLE_OK ) { return atoi( buffer.c_str() ); } return 0; } Hi there, first of all I'm having trouble debugging this in visual studio express 2008 so I'm unsure what buffer.c_str() might actually be returning but I am outputting 1 or 0 to the web page being posted to. Therefore I'm expecting the buffer to be one or the other, however I seem to only be returning 0 or equivalent. Does the code above look like it will return what I expect or should my variable types be different? The conversion using "atoi" may be an issue. Any thought would be much appreciated.

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  • Delphi dbExpress and Interbase: UTF8 migration steps and risks?

    - by mjustin
    Currently, our database uses Win1252 as the only character encoding. We will have to support Unicode in the database tables soon, which means we have to perform this migration for four databases and around 80 Delphi applications which run in-house in a 24/7 environment. Are there recommendations for database migrations to UTF-8 (or UNICODE_FSS) for Delphi applications? Some questions listed below. Many thanks in advance for your answers! are there tools which help with the migration of the existing databases (sizes between 250 MB and 2 GB, no Blob fields), by dumping the data, recreating the database with UNICODE_FSS or UTF-8, and loading the data back? are there known problems with Delphi 2009, dbExpress and Interbase 7.5 related to Unicode character sets? would you recommend to upgrade the databases to Interbase 2009 first? (This upgrade is planned but does not have a high priority) can we simply migrate the database and Delphi will handle the Unicode character sets automatically, or will we have to change all character field types in every Datamodule (dfm and source code) too? which strategy would you recommend to work on the migration in parallel with the normal development and maintenance of the existing application? The application runs in-house so development and database administration is done internally.

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  • ASP.Net Response Filter Causing SharePoint 2010 "Unexpected Error"

    - by Jason Weber
    Hello everyone, I'm debugging an HttpModule with an ASP.NET response filter. This dynamically rewrites portions of rendered SharePoint WCM pages. The publishing pages render fine in SP2007 on both Server 2003 and Server 2008. However the equivalent pages fail to render in SP2010 B2 on Server 2008 R2. The generic "An unexpected error has occurred message" page is displayed. This error only happens when the response filter is applied to an .aspx page. Other page types, such as .css, render fine on this platform. This error also happens when the response filter does not modify the page at all (pure pass-through). This KB article seems very closely related: http://support.microsoft.com/kb/2014472. However, this same error occurs with caching disabled. I see no related entries in any of the following: ULS for SP, Event Log, Failed Request Tracing (IIS7). Running under the debugger suggests that the custom code is not raising any exceptions. Any help or insight would be greatly appreciated.

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  • WCF service with PHP client - complex type as parameter not working

    - by Matt F
    Hi, I have a WCF service with three methods. Two of the methods return custom types (these work as expected), and the third method takes a custom type as a parameter and returns a boolean. When calling the third method via a PHP soap client it returns an 'Object reference not set to an instance of an object' exception. Example Custom Type: _ Public Class MyClass Private _propertyA As Double <DataMember()> _ Public Property PropertyA() As Double Get Return _propertyA End Get Set(ByVal value As Double) _propertyA = value End Set End Property Private _propertyB As Double <DataMember()> _ Public Property PropertyB() As Double Get Return _propertyB End Get Set(ByVal value As Double) _propertyB = value End Set End Property Private _propertyC As Date <DataMember()> _ Public Property PropertyC() As Date Get Return _propertyC End Get Set(ByVal value As Date) _propertyC = value End Set End Property End Class Method: Public Function Add(ByVal param As MyClass) As Boolean Implements IService1.Add ' ... End Function PHP client call: $client-Add(array('param'=array( 'PropertyA' = 1, 'PropertyB' = 2, 'PropertyC' = "2009-01-01" ))); The WCF service works fine with a .Net client but I'm new to PHP and can't get this to work. Is it possible to create an instance of 'MyClass' in PHP. Any help would be appreciated. Note: I'm using PHP 5 (XAMPP 1.7.0 for Windows). Thanks Matt

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  • Using Pylint with Django

    - by rcreswick
    I would very much like to integrate pylint into the build process for my python projects, but I have run into one show-stopper: One of the error types that I find extremely useful--:E1101: *%s %r has no %r member*--constantly reports errors when using common django fields, for example: E1101:125:get_user_tags: Class 'Tag' has no 'objects' member which is caused by this code: def get_user_tags(username): """ Gets all the tags that username has used. Returns a query set. """ return Tag.objects.filter( ## This line triggers the error. tagownership__users__username__exact=username).distinct() # Here is the Tag class, models.Model is provided by Django: class Tag(models.Model): """ Model for user-defined strings that help categorize Events on on a per-user basis. """ name = models.CharField(max_length=500, null=False, unique=True) def __unicode__(self): return self.name How can I tune Pylint to properly take fields such as objects into account? (I've also looked into the Django source, and I have been unable to find the implementation of objects, so I suspect it is not "just" a class field. On the other hand, I'm fairly new to python, so I may very well have overlooked something.) Edit: The only way I've found to tell pylint to not warn about these warnings is by blocking all errors of the type (E1101) which is not an acceptable solution, since that is (in my opinion) an extremely useful error. If there is another way, without augmenting the pylint source, please point me to specifics :) See here for a summary of the problems I've had with pychecker and pyflakes -- they've proven to be far to unstable for general use. (In pychecker's case, the crashes originated in the pychecker code -- not source it was loading/invoking.)

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  • Converting FoxPro Date type to SQL Server 2005 DateTime using SSIS

    - by Avrom
    Hi, When using SSIS in SQL Server 2005 to convert a FoxPro database to a SQL Server database, if the given FoxPro database has a date type, SSIS assumes it is an integer type. The only way to convert it to a dateTime type is to manually select this type. However, that is not practical to do for over 100 tables. Thus, I have been using a workaround in which I use DTS on SQL Server 2000 which converts it to a smallDateTime, then make a backup, then a restore into SQL Server 2005. This workaround is starting to be a little annoying. So, my question is: Is there anyway to setup SSIS so that whenever it encounters a date type to automatically assume it should be converted to a dateTime in SQL Server and apply that rule across the board? Update To be specific, if I use the import/export wizard in SSIS, I get the following error: Column information for the source and the destination data could not be retrieved, or the data types of source columns were not mapped correctly to those available on the destination provider. Followed by a list of a given table's date columns. If I manually set each one to a dateTime, it imports fine. But I do not wish to do this for a hundred tables.

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  • Emulating Dynamic Dispatch in C++ based on Template Parameters

    - by Jon Purdy
    This is heavily simplified for the sake of the question. Say I have a hierarchy: struct Base { virtual int precision() const = 0; }; template<int Precision> struct Derived : public Base { typedef Traits<Precision>::Type Type; Derived(Type data) : value(data) {} virtual int precision() const { return Precision; } Type value; }; I want a function like: Base* function(const Base& a, const Base& b); Where the specific type of the result of the function is the same type as whichever of first and second has the greater Precision; something like the following pseudocode: template<class T> T* operation(const T& a, const T& b) { return new T(a.value + b.value); } Base* function(const Base& a, const Base& b) { if (a.precision() > b.precision()) return operation((A&)a, A(b.value)); else if (a.precision() < b.precision()) return operation(B(a.value), (B&)b); else return operation((A&)a, (A&)b); } Where A and B are the specific types of a and b, respectively. I want f to operate independently of how many instantiations of Derived there are. I'd like to avoid a massive table of typeid() comparisons, though RTTI is fine in answers. Any ideas?

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  • F# and statically checked union cases

    - by Johan Jonasson
    Soon me and my brother-in-arms Joel will release version 0.9 of Wing Beats. It's an internal DSL written in F#. With it you can generate XHTML. One of the sources of inspiration have been the XHTML.M module of the Ocsigen framework. I'm not used to the OCaml syntax, but I do understand XHTML.M somehow statically check if attributes and children of an element are of valid types. We have not been able to statically check the same thing in F#, and now I wonder if someone have any idea of how to do it? My first naive approach was to represent each element type in XHTML as a union case. But unfortunately you cannot statically restrict which cases are valid as parameter values, as in XHTML.M. Then I tried to use interfaces (each element type implements an interface for each valid parent) and type constraints, but I didn't manage to make it work without the use of explicit casting in a way that made the solution cumbersome to use. And it didn't feel like an elegant solution anyway. Today I've been looking at Code Contracts, but it seems to be incompatible with F# Interactive. When I hit alt + enter it freezes. Just to make my question clearer. Here is a super simple artificial example of the same problem: type Letter = | Vowel of string | Consonant of string let writeVowel = function | Vowel str -> sprintf "%s is a vowel" str I want writeVowel to only accept Vowels statically, and not as above, check it at runtime. How can we accomplish this? Does anyone have any idea? There must be a clever way of doing it. If not with union cases, maybe with interfaces? I've struggled with this, but am trapped in the box and can't think outside of it.

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  • Beyond the @Produces annotation, how does Jersey (JAX-RS) know to treat a POJO as a specific mime ty

    - by hal10001
    I see a lot of examples for Jersey that look something like this: public class ItemResource { @GET @Path("/items") @Produces({"text/xml", "application/json"}) public List<Item> getItems() { List<Item> items = new ArrayList<Item>(); Item item = new Item(); item.setItemName("My Item Name!"); items.add(item); return items; } } But then I have trouble dissecting Item, and how Jersey knows how to translate an Item to either XML or JSON. I've seen very basic examples that just return a String of constructed HTML or XML, which makes more sense to me, but I'm missing the next step. I looked at the samples, and one of them stood out (the json-from-jaxb sample), since the object was marked with these types of annotations: @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "", propOrder = { "flight" }) @XmlRootElement(name = "flights") I'm looking for tutorials that cover this "translation" step-by-step, or an explanation here of how to translate a POJO to output as a specific mime type. Thanks!

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  • Considerations when architecting an application using Dependency Injection

    - by Dan Bryant
    I've begun experimenting with dependency injection (in particular, MEF) for one of my projects, which has a number of different extensibility points. I'm starting to get a feel for what I can do with MEF, but I'd like to hear from others who have more experience with the technology. A few specific cases: My main use case at the moment is exposing various singleton-like services that my extensions make use of. My Framework assembly exposes service interfaces and my Engine assembly contains concrete implementations. This works well, but I may not want to allow all of my extensions to have access to all of my services. Is there a good way within MEF to limit which particular imports I allow a newly instantiated extension to resolve? This particular application has extension objects that I repeatedly instantiate. I can import multiple types of Controllers and Machines, which are instantiated in different combinations for a Project. I couldn't find a good way to do this with MEF, so I'm doing my own type discovery and instantiation. Is there a good way to do this within MEF or other DI frameworks? I welcome input on any other things to watch out for or surprising capabilities you've discovered that have changed the way you architect.

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  • Need help in tuning a sql-query

    - by Viper
    Hello, i need some help to boost this SQL-Statement. The execution time is around 125ms. During the runtime of my program this sql (better: equally structured sqls for different tables) will be called 300.000 times. The average row count in the tables lies around 10.000.000 rows and new rows (updates/inserts) will be added with a timestamp each day. Data which are interesting for this particular export-program lies in the last 1-3 days. Maybe this is helpful for an index to create. The data i need is the current valid row for a given id and the forerunner datarow to get the updates (if exists). We use a Oracle 11g database and Dot.Net Framework 3.5 SQL-Statement to boost: select ID_SOMETHING, -- Number(12) ID_CONTRIBUTOR, -- Char(4 Byte) DATE_VALID_FROM, -- DATE DATE_VALID_TO -- DATE from TBL_SOMETHING XID where ID_SOMETHING = :ID_INSTRUMENT and ID_CONTRIBUTOR = :ID_CONTRIBUTOR and DATE_VALID_FROM <= :EXPORT_DATE and DATE_VALID_TO >= :EXPORT_DATE order by DATE_VALID_FROM asc; Here i uploaded the current Explain-Plan for this query. I'm not a database expert so i don't know which index-type would fit best for this requirement. I have seen that there are many different possible index-types which could be applied. Maybe Oracle Optimizer Hints are helpful, too. Does anyone has a good idea for tuning this sql or can point me in a right direction?

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  • C# client to Java web service

    - by tomislavg
    I have received wsdl file from outside company. I'm using VS2005 c#. With wsdl.exe I have created class containing methods and types for the given web service. To connect to the service outside company requires that certificate from the smart card is inputed in the header. I think i have achieved this with service.ClientCertificates.Add("Path to exported cert" - at least for now, after probably later i will take it from Certificate Store When service is called there are three steps that are taken and visible by the Fidller(Web Debugging Proxy)). service is called on the url http://test.company.com/webservice.wsdl service redirects the request to certificate server and pin needs to be inputed to get cookie for the server service is again redirected to url http://test.company.com/webservice.wsdl At point 1. I can see that my request send to the server contains .... but at point 3. i can not see request` just a empty string. The exception is thrown Msg: Possible SOAP version mismatch: Envelope namespace http://schemas.xmlsoap.org/wsdl/ was unexpected. Expecting http://schemas.xmlsoap.org/soap/envelope/. Does somebody have an example how to connect to java web service with certificate and AlowRedirect enabled for the web service? Any ideas what i am doing wrong are more that welcome.

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  • Codeplex/Sourceforge for internal use

    - by Josh
    I'm looking for a free/open source collaborative project manager that can be deployed internally in my workplace that would act similar to Codeplex or Sourceforge. Does anyone know of something like this, and if so do you have experience with it. Requirements: Open Source or Free Locally Deployable Has the same types of features found in Sourceforge / Codeplex Issue/Feature Tracking Community Interaction (ie. Voting, Roles, etc.) SCM Integration (Optional) .NET/Windows Friendly (Optional) Every business ends up having internal utilities, and domain specific apps that developers create to make life easier. Given the input of the internal developer community they have the potential to become much better (can you say GMail...), and I would simply like to foster such an environment internally by providing an easy place for that interaction to take place. UPDATE: So I like what I am seeing in both Trac and GForge, but both are heavily geared towards UNIX/Subversion environments. I should have specified this, but we are a MS shop from top to bottom. How practical do you think it is going to be to try and use these in a MS .NET environment? Would that be like trying to shove a square peg through a round hole?

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  • Which Project Management Software is adequate for Software & Non-Software Projects?

    - by cusack
    PMS = (Project Management Software) I used trac for software development some time ago. Right now I'm searching for a new more powerful (scheduling, gantt charts, ...) free solution (as in free beer ;-) and free to install on my server) for my current software project. Besides the current software project, abstract project management features like issue-tracking & scheduling would be great for coordinating a group of volunteers for real-life projects as well. I would want one solution for both purposes, so that I have the hassle of installation, getting used to the system and administration only once. So I tried redmine but the problem is it seems to be designed for software projects only. I can't suggest such a solution for the volunteer-group if tickets/issues would have to be of type bug, feature, ... I shortlisted the following six PMS from the wikipedia comparison http://en.wikipedia.org/wiki/List_of_project_management_software Project.net Project-Open Redmine Trac Endeavour Software Project Management eGroupWare I guess they are all more or less fine for software development but would you consider any of these to be good for the non-software project as well? Cliff Notes: I would want a start page situation like in trac. The start-page is a wiki presenting the project and not the PMS. But you can log into the PMS from there. Feature-wish list: wiki, Issue tracking, revision control, scheduling & gantt charts, forums (least important) (Btw: I'm very aware that I can't expect everything to be perfect ;-) 1.)Do you know a suitable solution for software and real-life projects or a highly customizable PMS where I can easily remove sth. like "browse source"(trac) and rename things like ticket/issue-types "bug", "feature"? 2.)Any experience good/bad with the above mentioned six PMS? I would personally guess that "Redmine" and "Endeavour Software Project Management" are too focused on software projects.

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  • Embedded non-relational (nosql) data store

    - by Igor Brejc
    I'm thinking about using/implementing some kind of an embedded key-value (or document) store for my Windows desktop application. I want to be able to store various types of data (GPS tracks would be one example) and of course be able to query this data. The amount of data would be such that it couldn't all be loaded into memory at the same time. I'm thinking about using sqlite as a storage engine for a key-value store, something like y-serial, but written in .NET. I've also read about FriendFeed's usage of MySQL to store schema-less data, which is a good pointer on how to use RDBMS for non-relational data. sqlite seems to be a good option because of its simplicity, portability and library size. My question is whether there are any other options for an embedded non-relational store? It doesn't need to be distributable and it doesn't have to support transactions, but it does have to be accessible from .NET and it should have a small download size. UPDATE: I've found an article titled SQLite as a Key-Value Database which compares sqlite with Berkeley DB, which is an embedded key-value store library.

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  • Is there a library that can decompile a method into an Expression tree, with support for CLR 4.0?

    - by Daniel Earwicker
    Previous questions have asked if it is possible to turn compiled delegates into expression trees, for example: http://stackoverflow.com/questions/767733/converting-a-net-funct-to-a-net-expressionfunct The sane answers at the time were: It's possible, but very hard and there's no standard library solution. Use Reflector! But fortunately there are some greatly-insane/insanely-great people out there who like reverse engineering things, and they make difficult things easy for the rest of us. Clearly it is possible to decompile IL to C#, as Reflector does it, and so you could in principle instead target CLR 4.0 expression trees with support for all statement types. This is interesting because it wouldn't matter if the compiler's built-in special support for Expression<> lambdas is never extended to support building statement expression trees in the compiler. A library solution could fill the gap. We would then have a high-level starting point for writing aspect-like manipulations of code without having to mess with raw IL. As noted in the answers to the above linked question, there are some promising signs but I haven't succeeded in finding if there's been much progress since by searching. So has anyone finished this job, or got very far with it? Note: CLR 4.0 is now released. Time for another look-see.

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  • howto distinguish composition and self-typing use-cases

    - by ayvango
    Scala has two instruments for expressing object composition: original self-type concept and well known trivial composition. I'm curios what situations I should use which in. There are obvious differences in their applicability. Self-type requires you to use traits. Object composition allows you to change extensions on run-time with var declaration. Leaving technical details behind I can figure two indicators to help with classification of use cases. If some object used as combinator for a complex structure such as tree or just have several similar typed parts (1 car to 4 wheels relation) than it should use composition. There is extreme opposite use case. Lets assume one trait become too big to clearly observe it and it got split. It is quite natural that you should use self-types for this case. That rules are not absolute. You may do extra work to convert code between this techniques. e.g. you may replace 4 wheels composition with self-typing over Product4. You may use Cake[T <: MyType] {part : MyType} instead of Cake { this : MyType => } for cake pattern dependencies. But both cases seem counterintuitive and give you extra work. There are plenty of boundary use cases although. One-to-one relations is very hard to decide with. Is there any simple rule to decide what kind of technique is preferable? self-type makes you classes abstract, composition makes your code verbose. self-type gives your problems with blending namespaces and also gives you extra typing for free (you got not just a cocktail of two elements but gasoline-motor oil cocktail known as a petrol bomb). How can I choose between them? What hints are there? Update: Let us discuss the following example: Adapter pattern. What benefits it has with both selt-typing and composition approaches?

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  • Querying a database using Cocoa.

    - by S1syphus
    Hello everybody. Before I start a disclaimer, I should add a little disclaimer, that I am relatively new to Cocoa development and C in general. However I do have a copy of 'Cocoa Programming for Mac OS X 3rd edition' by Aaron Hillegass, which I am working through and using as a base, if anybody has a copy I am using the 'AmaZone' example on page 346 as a template and base. I trying to develop a small client app that takes a search string then displays results from a database accordingly. The database will contain a: list of files, their location, description & creation date, so for the moment the field number and types will remain the same. After looking around on SO, I saw something like: NSURL *myURL = [NSURL URLWithString:@"http://www.myserver.com/results.php"]; NSArray *sqlResults = [[NSArray alloc] initWithContentsOfURL:myURL]; I've worked with php before, so my current thinking after seeing this is create a php script on the server that queries the database, and creates an XML output. And with the XML response, just parse it. Would this be ok? as is there any major pitfalls anybody can see, that I can't. I know there are some database bundles, I've had a look at BaseTen for Postgres, but being relatively new to this, didn't want to get in over my head. Or if anybody else has any other suggestions and ideas, they would be greatly appreciated.

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  • Is a "factory" method the right pattern?

    - by jdt141
    Hey all - So I'm working to improve an existing implementation. I have a number of polymorphic classes that are all composed into a higher level container class. The problem I'm dealing with at the moment is that the higher level container class, well, sucks. It looks something like this, which I really don't have a problem with (as the polymorphic classes in the container should be public). My real issue is the constructor... /* * class1 and class 2 derive from the same superclass */ class Container { public: boost::shared_ptr<ComposedClass1> class1; boost::shared_ptr<ComposedClass2> class2; private: ... } /* * Constructor - builds the objects that we need in this container. */ Container::Container(some params) { class1.reset(new ComposedClass1(...)); class2.reset(new ComposedClass2(...)); } What I really need is to make this container class more re-usable. By hard-coding up the member objects and instantiating them, it basically isn't and can only be used once. A factory is one way to build what I need (potentially by supplying a list of objects and their specific types to be created?) Other ways to get around this problem? Seems like someone should have solved it before... Thanks!

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  • Setting attributes of a class during construction from **kwargs

    - by Carson Myers
    Python noob here, Currently I'm working with SQLAlchemy, and I have this: from __init__ import Base from sqlalchemy.schema import Column, ForeignKey from sqlalchemy.types import Integer, String from sqlalchemy.orm import relationship class User(Base): __tablename__ = "users" id = Column(Integer, primary_key=True) username = Column(String, unique=True) email = Column(String) password = Column(String) salt = Column(String) openids = relationship("OpenID", backref="users") User.__table__.create(checkfirst=True) #snip definition of OpenID class def create(**kwargs): user = User() if "username" in kwargs.keys(): user.username = kwargs['username'] if "email" in kwargs.keys(): user.username = kwargs['email'] if "password" in kwargs.keys(): user.password = kwargs['password'] return user This is in /db/users.py, so it would be used like: from db import users new_user = users.create(username="Carson", password="1234") new_user.email = "[email protected]" users.add(new_user) #this function obviously not defined yet but the code in create() is a little stupid, and I'm wondering if there's a better way to do it that doesn't require an if ladder, and that will fail if any keys are added that aren't in the User object already. Like: for attribute in kwargs.keys(): if attribute in User: user.__attribute__[attribute] = kwargs[attribute] else: raise Exception("blah") that way I could put this in its own function (unless one hopefully already exists?) So I wouldn't have to do the if ladder again and again, and so I could change the table structure without modifying this code. Any suggestions?

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