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MSDN Library

CallingConvention Enumeration

Specifies the calling convention required to call methods implemented in unmanaged code.

Namespace:  System.Runtime.InteropServices
Assemblies:   System.Runtime.InteropServices (in System.Runtime.InteropServices.dll)
  mscorlib (in mscorlib.dll)

public enum CallingConvention

Member nameDescription
Supported by Portable Class LibraryCdeclThe caller cleans the stack. This enables calling functions with varargs, which makes it appropriate to use for methods that accept a variable number of parameters, such as Printf.
FastCallThis calling convention is not supported.
Supported by Portable Class LibraryStdCallThe callee cleans the stack. This is the default convention for calling unmanaged functions with platform invoke.
Supported by Portable Class LibraryThisCallThe first parameter is the this pointer and is stored in register ECX. Other parameters are pushed on the stack. This calling convention is used to call methods on classes exported from an unmanaged DLL.
Supported by the XNA FrameworkSupported by Portable Class LibraryWinapiThis member is not actually a calling convention, but instead uses the default platform calling convention. For example, on Windows the default is StdCall and on Windows CE.NET it is Cdecl.

Always use the CallingConvention enumeration rather than the CALLCONV enumeration to specify a calling convention in managed code. The latter exists only for the sake of COM definitions. The CallingConvention enumeration is used by DllImportAttribute and several classes in System.Reflection.Emit to dynamically emit platform invoke signatures.

The following example demonstrates how to apply the Cdecl calling convention, which you must use because the stack is cleaned up by the caller.

using System;
using System.Runtime.InteropServices;

public class LibWrap
// C# doesn't support varargs so all arguments must be explicitly defined. 
// CallingConvention.Cdecl must be used since the stack is  
// cleaned up by the caller. 

// int printf( const char *format [, argument]... )

[DllImport("msvcrt.dll", CharSet=CharSet.Unicode, CallingConvention=CallingConvention.Cdecl)]
public static extern int printf(String format, int i, double d); 

[DllImport("msvcrt.dll", CharSet=CharSet.Unicode, CallingConvention=CallingConvention.Cdecl)]
public static extern int printf(String format, int i, String s); 

public class App
    public static void Main()
        LibWrap.printf("\nPrint params: %i %f", 99, 99.99);
        LibWrap.printf("\nPrint params: %i %s", 99, "abcd");

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
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