DynamicMethod.CreateDelegate Method (Type, Object)
Completes the dynamic method and creates a delegate that can be used to execute it, specifying the delegate type and an object the delegate is bound to.
Assembly: mscorlib (in mscorlib.dll)
[<ComVisibleAttribute(true)>] abstract CreateDelegate : delegateType:Type * target:Object -> Delegate [<ComVisibleAttribute(true)>] override CreateDelegate : delegateType:Type * target:Object -> Delegate
- Type: System.Type
A delegate type whose signature matches that of the dynamic method, minus the first parameter.
- Type: System.Object
An object the delegate is bound to. Must be of the same type as the first parameter of the dynamic method.
Return ValueType: System.Delegate
A delegate of the specified type, which can be used to execute the dynamic method with the specified target object.
This method overload creates a delegate bound to a particular object. Such a delegate is said to be closed over its first argument. Although the method is static, it acts as if it were an instance method; the instance is target.
This method overload requires target to be of the same type as the first parameter of the dynamic method, or to be assignable to that type (for example, a derived class). The signature of delegateType has all the parameters of the dynamic method except the first. For example, if the dynamic method has the parameters String, Int32, and Byte, then delegateType has the parameters Int32 and Byte; target is of type String.
Calling the CreateDelegate method or the Invoke method completes the dynamic method. Any further attempt to alter the dynamic method, such as modifying parameter definitions or emitting more Microsoft intermediate language (MSIL), is ignored; no exception is thrown.
To create a method body for a dynamic method when you have your own MSIL generator, call the GetDynamicILInfo method to obtain a DynamicILInfo object. If you do not have your own MSIL generator, call the GetILGenerator method to obtain an ILGenerator object that can be used to generate the method body.
The following code example creates delegate that binds a DynamicMethod to an instance of a type, so that the method acts on the same instance each time it is invoked.
The code example defines a class named Example with a private field, a class named DerivedFromxample that derives from the first class, a delegate type named UseLikeStatic that returns Int32 and has parameters of type Example and Int32, and a delegate type named UseLikeInstance that returns Int32 and has one parameter of type Int32.
The example code then creates a DynamicMethod that changes the private field of an instance of Example and returns the previous value.
In general, changing the internal fields of classes is not good object-oriented coding practice.
The example code creates an instance of Example and then creates two delegates. The first is of type UseLikeStatic, which has the same parameters as the dynamic method. The second is of type UseLikeInstance, which lacks the first parameter (of type Example). This delegate is created using the method overload; the second parameter of that method overload is an instance of Example, in this case the instance just created, which is bound to the newly created delegate. Whenever that delegate is invoked, the dynamic method acts on the bound instance of Example.
This is an example of the relaxed rules for delegate binding introduced in the .NET Framework 2.0, along with new overloads of the Delegate.CreateDelegate method. For more information, see the Delegate class.
The UseLikeStatic delegate is invoked, passing in the instance of Example that is bound to the UseLikeInstance delegate. Then the UseLikeInstance delegate is invoked, so that both delegates act on the same instance of Example. The changes in the values of the internal field are displayed after each call. Finally, a UseLikeInstance delegate is bound to an instance of DerivedFromxample, and the delegate calls are repeated.