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CallingConventions Enumeration

May 11, 2014

Defines the valid calling conventions for a method.

This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.

Namespace:  System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

[FlagsAttribute]
public enum CallingConventions

Member nameDescription
AnySpecifies that either the Standard or the VarArgs calling convention may be used.
ExplicitThisSpecifies that the signature is a function-pointer signature, representing a call to an instance or virtual method (not a static method). If ExplicitThis is set, HasThis must also be set. The first argument passed to the called method is still a this pointer, but the type of the first argument is now unknown. Therefore, a token that describes the type (or class) of the this pointer is explicitly stored into its metadata signature.
HasThisSpecifies an instance or virtual method (not a static method). At run-time, the called method is passed a pointer to the target object as its first argument (the this pointer). The signature stored in metadata does not include the type of this first argument, because the method is known and its owner class can be discovered from metadata.
StandardSpecifies the default calling convention as determined by the common language runtime. Use this calling convention for static methods. For instance or virtual methods use HasThis.
VarArgsSpecifies the calling convention for methods with variable arguments.

The native calling convention is the set of rules governing the order and layout of arguments passed to compiled methods. It also governs how to pass the return value, what registers to use for arguments, and whether the called or the calling method removes arguments from the stack.

The following example finds specific overloads of MethodA, specifying binding constraints, calling conventions, and a variety of argument types.



using System;
using System.Reflection;

class Example
{
   // Methods to get:

   public void MethodA(int i, int j) { }

   public void MethodA(int[] i) { }

   public void MethodA(ref int r) { }

   // Method that takes an out parameter:
   public void MethodA(int i, out int o) { o = 100; }


   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      MethodInfo mInfo;

      // Get MethodA(int i, int j)
      mInfo = typeof(Example).GetMethod("MethodA",
          BindingFlags.Public | BindingFlags.Instance,
          null,
          CallingConventions.Any,
          new Type[] { typeof(int), typeof(int) },
          null);
      outputBlock.Text += String.Format("Found method: {0}", mInfo) + "\n";

      // Get MethodA(int[] i)
      mInfo = typeof(Example).GetMethod("MethodA",
          BindingFlags.Public | BindingFlags.Instance,
          null,
          CallingConventions.Any,
          new Type[] { typeof(int[]) },
          null);
      outputBlock.Text += String.Format("Found method: {0}", mInfo) + "\n";

      // Get MethodA(ref int r)
      mInfo = typeof(Example).GetMethod("MethodA",
          BindingFlags.Public | BindingFlags.Instance,
          null,
          CallingConventions.Any,
          new Type[] { typeof(int).MakeByRefType() },
          null);
      outputBlock.Text += String.Format("Found method: {0}", mInfo) + "\n";

      // Get MethodA(int i, out int o)
      mInfo = typeof(Example).GetMethod("MethodA",
          BindingFlags.Public | BindingFlags.Instance,
          null,
          CallingConventions.Any,
          new Type[] { typeof(int), typeof(int).MakeByRefType() },
          null);
      outputBlock.Text += String.Format("Found method: {0}", mInfo) + "\n";

   }
}

/* This method produces the following output:

Found method: Void MethodA(Int32, Int32)
Found method: Void MethodA(Int32[])
Found method: Void MethodA(Int32 ByRef)
Found method: Void MethodA(Int32, Int32 ByRef)
  */


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Supported in: 8.1, 8.0, 7.1, 7.0

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