C# Delegate Covariance

by Online Tutorials Library July 22, 2022

C# Delegates Covariance

C# Delegate Covariance allows us to call a method that has derived return type of the delegate signature return type.

It means we can call a method that returns parent or child class object.

Here, we are creating two examples. First example calls a method that returns a parent or derived class object.

C# Delegate Covariance Example 1

 using System; namespace CSharpFeatures {     class A { }     class B : A { }     class DelegateCoveriance     {         delegate A Mydelegate();         static void Main(string[] args)         {             // Calling MethodA             Mydelegate del = MethodA;             del();             // Calling MethodB             Mydelegate del2 = MethodB;             del2();         }         static A MethodA()         {             Console.WriteLine(“This is MethodA”);             return new A();         }         static B MethodB()         {             Console.WriteLine(“This is MethodB”);             return new B();         }     } } 

Output:

This is MethodA This is MethodB

C# Delegate Covariance Example 2

In this example, we are calling a method that does not return derived object as specified in delegate signature. Let’s see what happen, if we do this.

 using System; namespace CSharpFeatures {     class A { }     class B : A { }     class C { }     class DelegateCoveriance     {         delegate A Mydelegate();         static void Main(string[] args)         { // Delegating MethodA             Mydelegate del = MethodA;             del();             // Delegating MethodB             Mydelegate del2 = MethodB;             del2();             Mydelegate del3 = MethodC;             del3();         } static A MethodA()         {             Console.WriteLine(“This is MethodA”);             return new A();         } static B MethodB()         {             Console.WriteLine(“This is MethodB”);             return new B();         } static C MethodC()         {             Console.WriteLine(“This is MethodC”);         }     } } 

Output:

DelegateCoveriance.cs(25,31): error CS0407:  'CSharpFeatures.C CSharpFeatures.DelegateCoveriance.MethodC()' has the wrong return type

Next TopicC# Delegate Inference

beginners c class constructor example introduction loops object professionals properties statements static keyword structs this tutorial

C# Delegate Covariance

C# Delegates Covariance

C# Delegate Covariance Example 1

C# Delegate Covariance Example 2

Trigonometry MCQ (Multiple Choice Questions)

C# Exception Filters

You may also like