CallingConvention Enumeration (System.Runtime.InteropServices)

CallingConvention Enumeration

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This page is specific to

Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

CallingConvention Enumeration

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

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

Syntax

Visual Basic (Declaration)

<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Enumeration CallingConvention

Visual Basic (Usage)

Dim instance As CallingConvention

[SerializableAttribute]
[ComVisibleAttribute(true)]
public enum CallingConvention

Visual C++

[SerializableAttribute]
[ComVisibleAttribute(true)]
public enum class CallingConvention

JScript

public enum CallingConvention

Members

	Member name	Description
	Winapi	This 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.
	Cdecl	The 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.
	StdCall	The callee cleans the stack. This is the default convention for calling unmanaged functions with platform invoke.
	ThisCall	The 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.
	FastCall	This calling convention is not supported.

Remarks

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.

Examples

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

Visual Basic

Imports System
Imports Microsoft.VisualBasic
Imports System.Runtime.InteropServices

Public Class LibWrap
' Visual Basic does not 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)> _
Overloads Shared Function printf( _
    ByVal format As String, ByVal i As Integer, ByVal d As Double) As Integer
End Function

<DllImport("msvcrt.dll", CharSet:=CharSet.Unicode, CallingConvention:=CallingConvention.Cdecl)> _
Overloads Shared Function printf( _
    ByVal format As String, ByVal i As Integer, ByVal s As String) As Integer
End Function
End Class 'LibWrap

Public Class App
    Public Shared Sub Main()
        LibWrap.printf(ControlChars.CrLf + "Print params: %i %f", 99, _
                       99.99)
        LibWrap.printf(ControlChars.CrLf + "Print params: %i %s", 99, _
                       "abcd")
    End Sub 'Main
End Class 'App

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");
    }
}

Visual C++

using namespace System;
using namespace System::Runtime::InteropServices;
public ref class LibWrap
{
public:

   // 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)]
   static int printf( String^ format, int i, double d );

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

int main()
{
   LibWrap::printf( "\nPrint params: %i %f", 99, 99.99 );
   LibWrap::printf( "\nPrint params: %i %s", 99, "abcd" );
}

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Reference

System.Runtime.InteropServices Namespace

DllImportAttribute

System.Reflection.Emit