When I was marshalling EnumChildWindows, I declared the function like that: [DllImport("user32.dll",SetLastError=true)] public static extern bool EnumChildWindows( IntPtr hWndParent, User32Functions.EnumWindowsCallback lpEnumFunc, IntPtr lParam ); The point is, why do you need to pass a class or struct as the third parameter? I followed the MSDN recommendation and called the function like that: GCHandle gch=GCHandle.Alloc(this.twHandles); User32.EnumChildWindows(handleParent,this.enumThreadCallback,(IntPtr)gch); gch.Free(); Here this.twHandles is a text writer, which i later (in the callback function) use like so: private bool CaptureEnumThreadWindows(int handle, IntPtr param) { GCHandle gch=(GCHandle)param; TextWriter tw=(TextWriter)gch.Target; twHandles.Write(handle.ToString()+" "); twHandles.Flush(); return true; } Anyway, MSDN recommends to use GCHandle , 'so the delegate does not get moved by GC before the call ends, however I was trying to use without GCHandle, just passing IntPtr.Zero as the last parameter and it works anyway. Frankly I don't understand how this (GCHandle) can prevent the delegate from being moved by GC, but that's what MSDN says. (see GCHandle sample)

new FileInfo("myPath").Length

If we can use StreamReader or other managed call for asyncronous calls, then please let me know . how can i do the same. FileStream::BeginRead FileStream::EndRead

There are two ways you can call ReadFile: First way: import the function: [DllImport(S"Kernel32.dll", EntryPoint="ReadFile", CharSet=CharSet::Auto)] extern "C" Boolean ReadFileNative(IntPtr hFile,StringBuilder *lpBuffer, UInt32 nNumberOfBytesToRead, UInt32 *lpNumberOfBytesRead, Int32); Here's a function that returns text from a file: String *GetFileTextWithImport(String *fileName){ FileStream *fs=new FileStream(fileName,FileMode::Open); //Wrapping a handle with HandleRef guarantees that //the managed object is not garbage collected //until the platform invoke call completes. HandleRef hRef=HandleRef(fs,fs->Handle); StringBuilder *sbText=new StringBuilder(fs->Length); UInt32 uiToRead=0; ReadFileNative(hRef.Handle,sbText,fs->Length,&uiToRead,0); fs->Dispose(); return sbText->ToString(); } Second Way: just call ReadFile without importing String *GetFileText(String *fileName){ FileStream *fs=new FileStream(fileName,FileMode::Open); HandleRef hRef=HandleRef(fs,fs->Handle); IntPtr ptrText=Marshal::AllocHGlobal(fs->Length); DWORD uiToRead=fs->Length, uiRead=0; ReadFile((HANDLE)hRef.Handle,ptrText.ToPointer(),uiToRead,&uiRead,NULL); String *strRet=Marshal::PtrToStringAnsi(ptrText); Marshal::FreeHGlobal(ptrText); fs->Dispose(); return strRet; P.S. By the way, why not use the System.IO.StreamReader?

Here's a simple example: #using using namespace System; public __delegate Int32 FactorialCallback(Int32,Int32*); public __gc class Factorial{ public: FactorialCallback *fc; Factorial(){ this->fc=new FactorialCallback(this, GetFactorial); } Int32 GetFactorial(Int32 iSeed, Int32 *iNumberOfCircles){ (*iNumberOfCircles)++; return (iSeed==0)?1:(GetFactorial(iSeed-1,iNumberOfCircles)*iSeed); } Void FactorialComplete(IAsyncResult *ar){ Int32 iNumberOfCircles; Int32 iResult=this->fc->EndInvoke(&iNumberOfCircles,ar); Console::WriteLine(S"The result is {0}, nuber of circles is {1}",iResult.ToString(),(iNumberOfCircles-1).ToString()); Console::Read(); } }; int _tmain() { Factorial *fact=new Factorial(); Int32 dummy=0; AsyncCallback *ac=new AsyncCallback(fact,&Factorial::FactorialComplete); fact->fc->BeginInvoke(5,&dummy,ac,NULL); Console::WriteLine(S"Main complete"); Console::Read(); return 0; }

Could someone please help with marshalling to .NET. I posted this question here, not in C#, 'cause I know for sure the mistake is somewhere in .idl or cpp file. I have a Win32 C++ project with the following three files: //tlbsamp.cpp/////////////////////////////////////////////////// #include interface ITest{bool MyFunc();}; class Test:public ITest{ int i; public: Test(){i=10;} int MyFunc(){return i;} }; ITest* __stdcall MyDll_CreateTest(){ return new Test(); } int __stdcall MyDll_CreateInt(){ return rand();} BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved ) {return TRUE;} //tlbsamp.def////////////////////////////////////////////////////////// LIBRARY TLBSamp DESCRIPTION 'Sample DLL' EXPORTS MyDll_CreateTest MyDll_CreateInt //tlbsamp.idl///////////////////////////////////////////////////////////// import "oaidl.idl"; import "ocidl.idl"; [ uuid(983EE63A-7FB0-494a-AD63-14F48347DB7A), lcid(0x0409), version(1.0) ] library TLBSample { [object,uuid( 1F707072-05C6-4501-AD74-CFD57AB8002C)] interface ITest:IUnknown {int MyFunc ();} [ version(1.0), dllname("TLBSamp.dll")] module MyDllFunctions { [entry("MyDll_CreateTest")] ITest* __stdcall CreateTest(); [entry("MyDll_CreateInt")] int _stdcall CreateInt(); } }; I am compiling the project and get tlbsamp.dll ,tlbsamp.tlb, tlbsamp.lib, then I create a c# project, AddReference->COM-> Browse, all the .tlb file. In object browser I can see my ITest interface with MyFunk function. Here's the c# code. using System; using System.Runtime.InteropServices; using TLBSample; namespace Test_Call_MSDN_Dll { class Class1 { [DllImport(@"E:\MyProgs\NET\TLBSamp\debug\tlbsamp.dll")] public static extern TLBSample.ITest MyDll_CreateTest(); [DllImport(@"E:\MyProgs\NET\TLBSamp\debug\tlbsamp.dll")] public static extern Int32 MyDll_CreateInt(); [STAThread] static void Main(string[] args) { Console.WriteLine(MyDll_CreateInt().ToString());//OK-works fine ITest spClass=MyDll_CreateTest();//ExecutionEngineException(???) Console.WriteLine(spClass.MyFunc().ToString()); Сonsole.Read(); } } } What am I doing wrong? Thanks in advance!

Please have a look at the following log my application has made: 9:33:38Application Starting (Application_Start) 9:33:38Application variable 'server' is really null 9:33:39Session Starting (Session_Start) 9:37:12Application Starting (Application_Start) 9:37:12Application variable 'server' is really null 9:37:12Session Starting (Session_Start) So the question is how is it ever possible that another instance of my web application is starting after 5 min when I have session timeout set to 30 min? I have problem with that because in each case the application creates new instances of application items, so my application state is not syncronized. Thanks in advance!

Could anyone please advise me where I can find a source code sample (tutorial) of a chat application written using ASP.NET and C# (C++.NET). There is a number of good articles on this site, however all of them are either ASP or Winform or done in VB. Thanks in advance!

I meant, in this example no image quality loss can be observed.

Button button1=new Button(); button1.Parent=this; button1.Bounds=new Rectangle(20,20,256,256); button1.Image=new Bitmap(@"C:\Windows\soap bubbles.bmp"); FileStream fs=new FileStream("iconser.bin",FileMode.OpenOrCreate,FileAccess.Write,FileShare.None); BinaryFormatter bf=new BinaryFormatter(); bf.Serialize(fs,button1.Image); fs.Flush(); fs.Close(); FileStream fsOut=new FileStream("iconser.bin",FileMode.Open,FileAccess.Read,FileShare.None); Image img=(Image)bf.Deserialize(fsOut); Button btn=new Button(); btn.Bounds=new Rectangle(300,20,256,256); btn.Parent=this; btn.Image=img;