Type.DeclaringMethod Property

July 28, 2014

Gets a MethodBase that represents the declaring method, if the current Type represents a type parameter of a generic method.

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

public virtual MethodBase DeclaringMethod { get; }

Property Value

Type: System.Reflection.MethodBase
If the current Type represents a type parameter of a generic method, a MethodBase that represents declaring method; otherwise, null.

The declaring method is a generic method definition. That is, if DeclaringMethod does not return null, then DeclaringMethod.IsGenericMethodDefinition returns true.

The DeclaringType and DeclaringMethod properties identify the generic type definition or generic method definition in which the generic type parameter was originally defined:

  • If the DeclaringMethod property returns a MethodInfo, that MethodInfo represents a generic method definition, and the current Type object represents a type parameter of that generic method definition.

  • If the DeclaringMethod property returns null, then the DeclaringType property always returns a Type object representing a generic type definition, and the current Type object represents a type parameter of that generic type definition.

  • Getting the DeclaringMethod property on a type whose IsGenericParameter property is false throws an InvalidOperationException.

The MethodBase that is returned by the DeclaringMethod property is either a MethodInfo in the case of a generic method, or a ConstructorInfo in the case of a generic constructor.

For a list of the invariant conditions for terms used in generic reflection, see the IsGenericType property remarks.

The following code example defines a class that has a generic method, assigns a type argument to the method, and invokes the resulting constructed generic method. It also displays information about the generic method definition and the constructed method. When displaying information about the type parameters of the generic method definition, in the DisplayGenericMethodInfo method, the example code shows the value of the DeclaringMethod property for the method's generic type parameter.


using System;
using System.Reflection;

// Define a class with a generic method.
public class Test
{
   public static void Generic<T>(System.Windows.Controls.TextBlock outputBlock, T toDisplay)
   {
      outputBlock.Text += String.Format("\r\nHere it is: {0}", toDisplay) + "\n";
   }
}

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      outputBlock.Text += "\r\n--- Examine a generic method." + "\n";

      // Create a Type object representing class Test, and
      // get a MethodInfo representing the generic method.
      //
      Type ex = typeof(Test);
      MethodInfo mi = ex.GetMethod("Generic");

      DisplayGenericMethodInfo(outputBlock, mi);

      // Assign the int type to the type parameter of the Example 
      // method.
      //
      MethodInfo miConstructed = mi.MakeGenericMethod(typeof(int));

      DisplayGenericMethodInfo(outputBlock, miConstructed);

      // Invoke the method.
      object[] args = {outputBlock, 42};
      miConstructed.Invoke(null, args);

      // Invoke the method normally.
      Test.Generic<int>(outputBlock, 42);

      // Get the generic type definition from the closed method,
      // and show it's the same as the original definition.
      //
      MethodInfo miDef = miConstructed.GetGenericMethodDefinition();
      outputBlock.Text += String.Format("\r\nThe definition is the same: {0}",
          miDef == mi) + "\n";
   }

   private static void DisplayGenericMethodInfo(System.Windows.Controls.TextBlock outputBlock, MethodInfo mi)
   {
      outputBlock.Text += String.Format("\r\n{0}", mi) + "\n";

      outputBlock.Text += String.Format("\tIs this a generic method definition? {0}",
          mi.IsGenericMethodDefinition) + "\n";

      outputBlock.Text += String.Format("\tIs it a generic method? {0}",
          mi.IsGenericMethod) + "\n";

      outputBlock.Text += String.Format("\tDoes it have unassigned generic parameters? {0}",
          mi.ContainsGenericParameters) + "\n";

      // If this is a generic method, display its type arguments.
      //
      if (mi.IsGenericMethod)
      {
         Type[] typeArguments = mi.GetGenericArguments();

         outputBlock.Text += String.Format("\tList type arguments ({0}):",
             typeArguments.Length) + "\n";

         foreach (Type tParam in typeArguments)
         {
            // IsGenericParameter is true only for generic type
            // parameters.
            //
            if (tParam.IsGenericParameter)
            {
               outputBlock.Text += String.Format("\t\t{0}  parameter position {1}" +
                   "\n\t\t   declaring method: {2}",
                   tParam,
                   tParam.GenericParameterPosition,
                   tParam.DeclaringMethod) + "\n";
            }
            else
            {
               outputBlock.Text += String.Format("\t\t{0}", tParam) + "\n";
            }
         }
      }
   }
}

/* This example produces the following output:

--- Examine a generic method.

Void Generic[T](T)
        Is this a generic method definition? True
        Is it a generic method? True
        Does it have unassigned generic parameters? True
        List type arguments (1):
                T  parameter position 0
                   declaring method: Void Generic[T](T)

Void Generic[Int32](Int32)
        Is this a generic method definition? False
        Is it a generic method? True
        Does it have unassigned generic parameters? False
        List type arguments (1):
                System.Int32

Here it is: 42

Here it is: 42

The definition is the same: True

 */


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

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