Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Export (0) Print
Expand All
Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

Generic Delegates (Visual C++)

You can use generic type parameters with delegates. For more information on delegates, see delegate.

generic < [class | typename] type-parameter-identifiers >
[accessibility-modifiers] delegate result-type identifier  

attributes (Optional)

Additional declarative information. For more information on attributes and attribute classes, see Attributes.


Comma-separated list of identifiers for the type parameters.


Takes the form specified in Constraints

accessibility-modifiers (Optional)

Accessibility modifiers (e.g. public, private).


The return type of the delegate.


The name of the delegate.

formal-parameters (Optional)

The parameter list of the delegate.

The type-parameter-identifiers are specified at the point where a delegate object is created. Both the delegate and method associated with it must have the same signature. The following is an example of a generic delegate declaration.

// generics_generic_delegate1.cpp
// compile with: /clr /c
generic < class ItemType>
delegate ItemType GenDelegate(ItemType p1, ItemType% p2);

The following sample shows that

  • You cannot use the same delegate object with different constructed types. Create different delegate objects for different types.

  • A generic delegate can be associated with a generic method.

  • When a generic method is called without specifying type arguments, the compiler tries to infer the type arguments for the call.

// generics_generic_delegate2.cpp
// compile with: /clr
generic < class ItemType>
delegate ItemType GenDelegate(ItemType p1, ItemType% p2);

generic < class ItemType>
ref struct MyGenClass {
   ItemType MyMethod(ItemType i, ItemType % j) {
      return ItemType();

ref struct MyClass {
   generic < class ItemType>
   static ItemType MyStaticMethod(ItemType i, ItemType % j) {
      return ItemType();

int main() {
   MyGenClass<int> ^ myObj1 = gcnew MyGenClass<int>();
   MyGenClass<double> ^ myObj2 = gcnew MyGenClass<double>();
   GenDelegate<int>^ myDelegate1 =
      gcnew GenDelegate<int>(myObj1, &MyGenClass<int>::MyMethod);

   GenDelegate<double>^ myDelegate2 = 
      gcnew GenDelegate<double>(myObj2, &MyGenClass<double>::MyMethod);

   GenDelegate<int>^ myDelegate =
      gcnew GenDelegate<int>(&MyClass::MyStaticMethod<int>);

The following example declares a generic delegate GenDelegate<ItemType>, and then instantiates it by associating it to the method MyMethod that uses the type parameter ItemType. Two instances of the delegate (an integer and a double) are created and invoked.

// generics_generic_delegate.cpp
// compile with: /clr
using namespace System;

// declare generic delegate
generic <typename ItemType>
delegate ItemType GenDelegate (ItemType p1, ItemType% p2);

// Declare a generic class:
generic <typename ItemType>
ref class MyGenClass {
   ItemType MyMethod(ItemType p1, ItemType% p2) {
      p2 = p1;
      return p1;

int main() {
   int i = 0, j = 0; 
   double m = 0.0, n = 0.0;

   MyGenClass<int>^ myObj1 = gcnew MyGenClass<int>();
   MyGenClass<double>^ myObj2 = gcnew MyGenClass<double>(); 

   // Instantiate a delegate using int.
   GenDelegate<int>^ MyDelegate1 = 
      gcnew GenDelegate<int>(myObj1, &MyGenClass<int>::MyMethod);

   // Invoke the integer delegate using MyMethod.
   i = MyDelegate1(123, j);

      "Invoking the integer delegate: i = {0}, j = {1}", i, j);

   // Instantiate a delegate using double.
   GenDelegate<double>^ MyDelegate2 = 
      gcnew GenDelegate<double>(myObj2, &MyGenClass<double>::MyMethod);

   // Invoke the integer delegate using MyMethod.
   m = MyDelegate2(0.123, n);

      "Invoking the double delegate: m = {0}, n = {1}", m, n);
Invoking the integer delegate: i = 123, j = 123 Invoking the double delegate: m = 0.123, n = 0.123

Community Additions

© 2015 Microsoft