Combine Method (Delegate, Delegate)
Collapse the table of content
Expand the table of content

Delegate.Combine Method (Delegate, Delegate)

 

Concatenates the invocation lists of two delegates.

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

public static Delegate Combine(
	Delegate a,
	Delegate b
)

Parameters

a
Type: System.Delegate

The delegate whose invocation list comes first.

b
Type: System.Delegate

The delegate whose invocation list comes last.

Return Value

Type: System.Delegate

A new delegate with an invocation list that concatenates the invocation lists of a and b in that order. Returns a if b is null, returns b if a is a null reference, and returns a null reference if both a and b are null references.

Exception Condition
ArgumentException

Both a and b are not null, and a and b are not instances of the same delegate type.

The invocation list can contain duplicate entries; that is, entries that refer to the same method on the same object.

System_CAPS_noteNote

Generic delegates that are assignment-compatible because of variance are not necessarily combinable. To be combinable, the types must match exactly. For example, suppose that a class named Derived is derived from a class named Base. A delegate of type Action<Base> (Action(Of Base) in Visual Basic) can be assigned to a variable of type Action<Derived>, as explained in Covariance and Contravariance in Generics, but the two delegates cannot be combined because the types do not match exactly.

Combine is useful for creating event handlers that call multiple methods each time an event occurs.

ReflectionPermission

when invoked late-bound through mechanisms such as Type.InvokeMember. Associated enumeration: ReflectionPermissionFlag.MemberAccess

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Return to top
Show:
© 2016 Microsoft