The System.MulticastDelegate and System.Delegate Base Classes

So, when you build a type using the C# delegate keyword, you indirectly declare a class type that derives from System.MulticastDelegate. This class provides descendents with access to a list that contains the addresses of the methods maintained by the delegate object, as well as several additional methods (and a few overloaded operators) to interact with the invocation list. Here are some select members of System.MulticastDelegate:

public abstract class MulticastDelegate : Delegate
{
    // Returns the list of methods "pointed to."
    public sealed override Delegate[] GetInvocationList();

    // Overloaded operators.
    public static bool operator ==(MulticastDelegate d1, MulticastDelegate d2);
    public static bool operator !=(MulticastDelegate d1, MulticastDelegate d2);

    // Used internally to manage the list of methods maintained by the delegate.
    private IntPtr _invocationCount;
    private object _invocationList;
}

System.MulticastDelegate obtains additional functionality from its parent class, System.Delegate. Here is a partial snapshot of the class definition:

public abstract class Delegate : ICloneable, ISerializable
{
    // Methods to interact with the list of functions.
    public static Delegate Combine(params Delegate[] delegates);
    public static Delegate Combine(Delegate a, Delegate b);
    public static Delegate Remove(Delegate source, Delegate value);
    public static Delegate RemoveAll(Delegate source, Delegate value);

    // Overloaded operators.
    public static bool operator ==(Delegate d1, Delegate d2);
    public static bool operator !=(Delegate d1, Delegate d2);

    // Properties that expose the delegate target.
    public MethodInfo Method { get; }
    public object Target { get; }
}

Now, understand that you can never directly derive from these base classes in your code (it is a compiler error to do so). Nevertheless, when you use the delegate keyword, you have indirectly created a class that “is-a” MulticastDelegate. Table 11-1 documents the core members common to all delegate types.

Table 11-1. Select Members of System.MultcastDelegate/System.Delegate