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  • Lambda expressions and nullable types

    - by Mathew
    I have two samples of code. One works and returns the correct result, one throws a null reference exception. What's the difference? I know there's some magic happening with capturing variables for the lambda expression but I don't understand what's going on behind the scenes here. int? x = null; bool isXNull = !x.HasValue; // this works var result = from p in data.Program where (isXNull) select p; return result.Tolist(); // this doesn't var result2 = from p in data.Program where (!x.HasValue) select p; return result2.ToList();

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  • Custom setter methods in Core-Data

    - by andrewebling
    I need to write a custom setter method for a field (we'll call it foo) in my subclass of NSManagedObject. foo is defined in the data model and Xcode has autogenerated @property and @dynamic fields in the .h and .m files respectively. If I write my setter like this: - (void)setFoo: (NSObject *)inFoo { [super setFoo: inFoo]; [self updateStuff]; } then I get a compiler warning on the call to super. Alternatively, if I do this: - (void)setFoo: (NSObject *)inFoo { [super setValue: inFoo forKey: inFoo]; [self updateStuff]; } then I end up in an infinite loop. So what's the correct approach to write a custom setter for a subclass of NSManagedObject?

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  • Showing custom model validation exceptions in the Django admin site.

    - by Guy Bowden
    I have a booking model that needs to check if the item being booked out is available. I would like to have the logic behind figuring out if the item is available centralised so that no matter where I save the instance this code validates that it can be saved. At the moment I have this code in a custom save function of my model class: def save(self): if self.is_available(): # my custom check availability function super(MyObj, self).save() else: # this is the bit I'm stuck with.. raise forms.ValidationError('Item already booked for those dates') This works fine - the error is raised if the item is unavailable, and my item is not saved. I can capture the exception from my front end form code, but what about the Django admin site? How can I get my exception to be displayed like any other validation error in the admin site?

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  • Force Response to Download File(s) to Desktop with Ruby?

    - by viatropos
    I was thinking about making a little crop/resize batch processor online, and wanted to know if there was a way for me to do the following: upload image and specify dimensions click "process" and remote app resizes image image downloads automatically locally to wherever it was I uploaded it (say from my desktop), but with a new name (based on the time for example). This would make it so I could host a free image processor that never stored any data other than tempfiles. Is that possible? Something like Rails' send_file method, but I'm using Sinatra and am looking for something in pure ruby. What's the basic concept behind this? What if I wanted to do this for multiple files? Åssuming I can get multiple files uploaded no problem, how can I download all of them automatically?

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  • How to retain one million simultaneous TCP connections?

    - by cow
    I am to design a server that needs to serve millions of clients that are simultaneously connected with the server via TCP. The data traffic between the server and the clients will be sparse, so bandwidth issues can be ignored. One important requirement is that whenever the server needs to send data to any client it should use the existing TCP connection instead of opening a new connection toward the client (because the client may be behind a firewall). Does anybody know how to do this, and what hardware/software is needed (at the least cost)? Thanks in advance for any suggestions.

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  • Why size_t arguments in template declaration need to be const?

    - by ArunSaha
    I can have std::bitset< 10 > bitsetA; or const size_t LengthB = 20; std::bitset< LengthB > bitsetB; without any problem. But, if the length is not const size_t LengthC = 30; std::bitset< LengthC > bitsetC; // Line 30, say I face the following compilation error 'LengthC' cannot appear in a constant-expression template argument 1 is invalid What is the reason for that? What would be the problem, for compiler and for user code, if line 30 was to be accepted? Is it because LengthC might have some alias?

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  • How to include header files in Visual Studio 2008?

    - by Sergio
    I am currently trying to compile a simple program that includes two header files. I see them in the Solution Explorer, where I included them through "include existing files". However, when I run my program it get the following error. fatal error C1083: Cannot open include file: 'FileWrite.h': No such file or directory. THe problem is that I see the file included in the Header's folder and in the code I have written: #include "FileWrite.h" and then the rest of the program code. Is there something else needed to do so that the compiler can see the header file and link it to the .cpp file I'm trying to compile?

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  • Running ASP.NET MVC 1.0 application

    - by Jack Daniels
    Hello I'm trying to build an app with ASP.NET MVC 1.0. I already have installed MVC 1.0 but after running the application It trows an exception: Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. Compiler Error Message: CS1705: Assembly 'MVC_CustomControls, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' uses 'System.Web.Routing, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' which has a higher version than referenced assembly 'System.Web.Routing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' Any help is greatly appreciated.

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  • C++/CLI value class constraint won't compile. Why?

    - by Simon
    Hello, a few weeks ago a co-worker of mine spent about two hours finding out why this piece of C++/CLI code won't compile with Visual Studio 2008 (I just tested it with Visual Studio 2010... same story). public ref class Test { generic<class T> where T : value class void MyMethod(Nullable<T> nullable) { } }; The compiler says: Error 1 error C3214: 'T' : invalid type argument for generic parameter 'T' of generic 'System::Nullable', does not meet constraint 'System::ValueType ^' C:\Users\Simon\Desktop\Projektdokumentation\GridLayoutPanel\Generics\Generics.cpp 11 1 Generics Adding ValueType will make the code compile. public ref class Test { generic<class T> where T : value class, ValueType void MyMethod(Nullable<T> nullable) { } }; My question is now. Why? What is the difference between value class and ValueType?

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  • How do I get a title or some text to appear in a Silverlight mediaplayer when switching to FullScree

    - by Matt
    I am working on an ASP.NET website with VB.NET code-behind. I have a Silverlight mediaplayer object on one of the pages and the user may view that video in FullScreen mode. When changing to full-screen mode they are losing the title and chapter of the video series they are viewing. I have tried accessing properties and searched the web for examples on how I could put a title or some text over the player when in FullScreen mode to give the user an indication of where they are currently at while viewing each video. I am using OnClientMediaEnded to move through the videos after each video has ended so they are able to watch the whole series once in FullScreen mode. I am using a call to javascript in with this method to do that and want to know if there is any way to get a title or text up there and then change once the video switches to the next in the series? The controls on the player also go away when going into FullScreen mode so any help with that would be greatly appreciated as well. Thanks

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  • Listbox that when you reach the end it goes back to the beginning

    - by Roy
    Hi, Is there a way to make a Listbox go back to the beginning of the list once a user scrolls all the way to the end of list? Current aspx code: <ListBox x:Name="listbox"> <ListBox.ItemTemplate> <DataTemplate> <Image Name="imgSource" Source="{Binding Path=Url}" /> </DataTemplate> </ListBox.ItemTemplate> </ListBox> Current code behind code: public class ImageScroller { public string Url { get; set; } } public MainPage() { InitializeComponent(); LoadImages(); } void LoadImages() { listbox.ItemsSource = new List<ImageScroller> { new ImageScroller { Url = "images/Chrysanthemum.jpg" }, new ImageScroller { Url = "images/Desert.jpg" }, new ImageScroller { Url = "images/Hydrangeas.jpg" }, }; } Thanks for your help!

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  • Is there a good collection library for C-language?

    - by matti
    We have to maintain and even develop C-code of our legacy system. Is there good collection library that would support Java/C# (new versions) style collections. Hashtable, HashSet, etc. Of course without objects, but with structs. The HashTable key limitations to "strings" and ints is not a problem. It wouldn't be bad if it's free even for commercial use. I'm back to C from C# and I must say i'm depressed using our own libraries and the language in general. We're using VS2005 and MS C-compiler if that has nothing to do with anything. Thanks & BR -Matti

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  • ToList()-- Does it Create a New List?

    - by Ngu Soon Hui
    Let's say I have a class public class MyObject { public int SimpleInt{get;set;} } And I have a List<MyObject>, and I ToList() it and then change one of the SimpleInt, will my change be propagated back to the original list. In other words, what would be the output of the following method? public void RunChangeList() { var objs = new List<MyObject>(){new MyObject(){SimpleInt=0}}; var whatInt = ChangeToList(objs ); } public int ChangeToList(List<MyObject> objects) { var objectList = objects.ToList(); objectList[0].SimpleInt=5; return objects[0].SimpleInt; } Why? P/S: I'm sorry if it seems obvious to find out. But I don't have compiler with me now...

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  • How to pass around event as parameter in c#

    - by Jerry Liu
    Am writing unit test for a multi-threading application, where I need to wait until a specific event triggered so that I know the asyn operation is done. E.g. When I call repository.add(something), I wait for event AfterChange before doing any assertion. So I write a util function to do that. public static void SyncAction(EventHandler event_, Action action_) { var signal = new object(); EventHandler callback = null; callback = new EventHandler((s, e) => { lock (signal) { Monitor.Pulse(signal); } event_ -= callback; }); event_ += callback; lock (signal) { action_(); Assert.IsTrue(Monitor.Wait(signal, 10000)); } } However, the compiler prevents from passing event out of the class. Is there a way to achieve that?

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  • Doing a SetLength on an array passed into a proc by reference

    - by csharpdefector
    Hi All, Sure, even I can do this... var testarray : array of string; setlength(testarray, 5); but if I want to get clever and have a procedure into which I pass the array by referance like this I cant do it! procedure DoStuffWithArray(var passedarray : array of string); begin setlength(passedarray, 5); end; compiler says 'incompatible types' on the single line of code in my proc. I can do other stuff on the array like set set element values if i do a setlength before i call the proc, but I cannot do the setlength in my proc, which is what I want to do. Any help much appreciated, thanks all.

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  • C/C++ usage of special CPU fetures

    - by b-gen-jack-o-neill
    Hi, I am curious, do new compilers use some extra features built into new CPUs such as MMX SSE,3DNow! and so? I mean, in original 8086 there was even no FPU, so compiler that old cannot even use it, but new compilers can, since FPU is part of every new CPU. So, does new compilers use new features of CPU? Or, it should be more right to ask, does new C/C++ standart library functions use new features? Thanks for answer.

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  • How can I bind dynamic data to DataGridTemplateColun in code?

    - by TuomoT
    I'm using DataGrid from CodePlex. I have objects (ICustomTypeDescriptor) that have properties 'name' 'description' 'c' 'd' and so on (the names are dynamic, and so is the value) and they have information behind them. I have templates for different types. And if I have to list the properties of a single element I can just bind to the values in xaml and use datatemplateselector (in datagridtemplatecolumn) which will pick the correct template. However, when I'm listing several of the elements, how can I use the selectors and the templates? How do I get the correct property bound to the template (two-way)? When ignoring the need for different templates, using DataGridTextColumn with bindings is very simple (and works, see example below), is there any way to use similar approach with the DataGridTemplateColumn? foreach (String propertyName in listOfPropertyNames) { DataGridTextColumn textColumn = new DataGridTextColumn() { Header = propertyName, Binding = new Binding() { Path = new PropertyPath(propertyName) } }; DataGrid.Columns.Add(textColumn); }

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  • Win32 script environment for testing http redirects?

    - by Anders Lindahl
    The past few days I've been working with setting up an Apache server on Windows. The server is supposed to host several .htaccess files, each redirecting (or, in some cases, proxying) to different hosts. I want to create tests for these redirectons, and the solution I'm currently considering is a CGI script running on the same server, sending GET requests to it and verifying that it gets the correct redirection headers back. A scripting solution (vscript/jscript) seems worth exploring, but so far I've only managed to rule out Microsoft.XMLHTTP because it follows the redirect "behind the scenes". Are there any libraries or other solutions already present on a reasonably standard Windows Server that can do this kind of low-level HTTP work? If not, any other suggestions of simple environments to set up for verifying redirects?

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  • Version resource in DLL not visible with right-click

    - by abunetta
    I'm trying to do something which is very easy to do in the regular MSVC, but not supported easily in VC++ Express. There is no resource editor in VC++ Express. So I added a file named version.rc into my DLL project. The file has the below content, which is compiled by the resource compiler and added to the final DLL. This resource is viewable in the DLL using reshacker, though not when right-clicking the DLL in Windows Explorer. What is missing from my RC file to make it appear when right-clicking? VS_VERSION_INFO VERSIONINFO FILEVERSION 1,0,0,1 PRODUCTVERSION 1,0,0,1 FILEFLAGSMASK 0x17L #ifdef _DEBUG FILEFLAGS 0x1L #else FILEFLAGS 0x0L #endif FILEOS 0x4L FILETYPE 0x1L FILESUBTYPE 0x0L BEGIN BLOCK "StringFileInfo" BEGIN BLOCK "040904b0" BEGIN VALUE "FileDescription", "something Application" VALUE "FileVersion", "1, 0, 0, 1" VALUE "InternalName", "something" VALUE "LegalCopyright", "Copyright (C) 2008 Somebody" VALUE "OriginalFilename", "something.exe" VALUE "ProductName", "something Application" VALUE "ProductVersion", "1, 0, 0, 1" END END BLOCK "VarFileInfo" BEGIN VALUE "Translation", 0x409, 1200 END END

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  • How do the do that? Transparent foreground on a web page

    - by Jim Beam
    I really can't find the right Google terms to track this down. But you're all quite smart so thought I'd post it here. You know how sometimes you are on a good site and you click a button (like to submit a form) and the form doesn't go away, instead, the foreground becomes transparent and it contains a message of some kind, or another page. The message is at the forefront but the previous page is still mostly visible behind it - how do they do that? I'm assuming it's an AJAX-esque trick.

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  • Display different xsl:attribute depending on the code

    - by Johann
    Dear All, I have the following xsl code in an xsl document <A target="_blank" style="text-decoration=none"> <xsl:attribute name="href">viewdoc.aspx?doc=<xsl:value-of select="URLFilePath"/>&amp;mode=inline</xsl:attribute> <xsl:attribute name="prefix"><xsl:value-of select="FileName"/>: </xsl:attribute> <IMG src="images/word_small.gif" border="0"/> </A> and in the code-behind I am doing this newItemNode = xmlDocument.CreateElement("URLFilePath") newItemNode.InnerText = correctedPath xmlItemNode.ParentNode.AppendChild(newItemNode) Now that works fine for word documents. However I need a way in code to check the extension of the file, and display the correct Image and xsl:attribute depending on the If statement. So the If statement will be like this:- If correctedPath.ToLower.Contains(".doc") Then //display the word icon and attributes Else //display the excel icon and attributes End If Can you please give me some tips and help on how I can achieve this? Thanks

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  • How to create a fully qualified hyperlink to a resource dynamically?

    - by Slauma
    In ASP.NET I'd like to create a link which points to a specific Uri and send this link in an email to a user, for instance something like http://www.BlaBla.com/CustomerPortal/Order/9876. I can create the second part of the Uri /CustomerPortal/Order/9876 dynamically in code-behind. My question is: How can I create the base Uri http://www.BlaBla.com without hardcoding it in my application? Basically I want to have something like: http://localhost:1234/CustomerPortal/Order/9876 (on my development machine) http://testserver/CustomerPortal/Order/9876 (on an internal test server) http://www.BlaBla.com/CustomerPortal/Order/9876 (on the production server) So is there a way to ask the server where the application is running: "Please tell me the base Uri of the application" ? Or any other way? Thank you in advance!

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  • An easy way to replace fread()'s with reading from a byte array?

    - by Sam Washburn
    I have a piece of code that needs to be run from a restricted environment that doesn't allow stdio (Flash's Alchemy compiler). The code uses standard fopen/fread functions and I need to convert it to read from a char* array. Any ideas on how to best approach this? Does a wrapper exist or some library that would help? Thanks! EDIT: I should also mention that it's reading in structs. Like this: fread(&myStruct, 1, sizeof(myStruct), f);

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  • How to use a delay in a swing application

    - by M.R.
    I am building a swing application. At some point, I have to start an "animation": ... jpanel1.setBackground(Color.Black); Delay(milli) jpanel1.setBackground(Color.White); ... and so on. The gui itself and all the logic behind it work.It is just this time depended color-changing that does not. I have read, that swing is not thread safe, but all the examples I found showed me how to start another thread (for example in the background) but never how to stop the current swing-gui thread.

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  • ASP.NET in VS IDE gives "Expression cannot be evaluated at this time."

    - by S Nash
    I read all of similar questions in SO but none seem to be an answer. Situation is simple. I have a ASP.NET webpage, In a VB code behind file I have the following line: iRendProvider = ddlProvider.SelectedItem.Value where iRendProvider is integer and ddlProvider is a dropdownlist. I put a breakpoint at the above line and code stops there. Now in the immdediate window in I type: ? ddlProvider.SelectedItem.Value I get "Expression cannot be evaluated at this time." If I step over iRendProvider = ddlProvider.SelectedItem.Value To the next line and I type ? iRendProvider , I see the correct value in the immediate window. Question is why this error and how to see contents of ddlProvider.

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