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Chapter ‎18   Unsafe code

create a delegate. If the argument is a value of a delegate-type, it identifies a delegate instance of which to create a copy.

The compile-time processing of a delegate-creation-expression of the form new D(E), where D is a delegate-type and E is an expression, consists of the following steps:

If E is a method group:

The set of methods identified by E must include exactly one method that is compatible (§‎15.1) with D, and this method becomes the one to which the newly created delegate refers. If no matching method exists, or if more than one matching method exists, a compile-time error occurs. If the selected method is an instance method, the instance expression associated with E determines the target object of the delegate.

As in a method invocation, the selected method must be compatible with the context of the method group: If the method is a static method, the method group must have resulted from a simple-name or a member-access through a type. If the method is an instance method, the method group must have resulted from a simple-name or a member-access through a variable or value. If the selected method does not match the context of the method group, a compile-time error occurs.

The result is a value of type D, namely a newly created delegate that refers to the selected method and target object.

Otherwise, if E is a value of a delegate-type:

D and E must be compatible (§‎15.1); otherwise, a compile-time error occurs.

The result is a value of type D, namely a newly created delegate that refers to the same invocation list as E.

Otherwise, the delegate creation expression is invalid, and a compile-time error occurs.

The run-time processing of a delegate-creation-expression of the form new D(E), where D is a delegate-type and E is an expression, consists of the following steps:

If E is a method group:

If the method selected at compile-time is a static method, the target object of the delegate is null. Otherwise, the selected method is an instance method, and the target object of the delegate is determined from the instance expression associated with E:

The instance expression is evaluated. If this evaluation causes an exception, no further steps are executed.

If the instance expression is of a reference-type, the value computed by the instance expression becomes the target object. If the target object is null, a System.NullReferenceException is thrown and no further steps are executed.

If the instance expression is of a value-type, a boxing operation (§‎4.3.1) is performed to convert the value to an object, and this object becomes the target object.

A new instance of the delegate type D is allocated. If there is not enough memory available to allocate the new instance, a System.OutOfMemoryException is thrown and no further steps are executed.

The new delegate instance is initialized with a reference to the method that was determined at compile-time and a reference to the target object computed above.

If E is a value of a delegate-type:

E is evaluated. If this evaluation causes an exception, no further steps are executed.

If the value of E is null, a System.NullReferenceException is thrown and no further steps are executed.

A new instance of the delegate type D is allocated. If there is not enough memory available to allocate the new instance, a System.OutOfMemoryException is thrown and no further steps are executed.

Copyright Microsoft Corporation 1999-2003. All Rights Reserved.133

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