MulticastDelegate Class
Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.
Assembly: mscorlib (in mscorlib.dll)
The MulticastDelegate type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | MulticastDelegate(Object, String) | Initializes a new instance of the MulticastDelegate class. |
![]() | MulticastDelegate(Type, String) | Initializes a new instance of the MulticastDelegate class. |
| Name | Description | |
|---|---|---|
![]() ![]() | Clone | Creates a shallow copy of the delegate. (Inherited from Delegate.) |
![]() ![]() | CombineImpl | Combines this Delegate with the specified Delegate to form a new delegate. (Overrides Delegate::CombineImpl(Delegate).) |
![]() ![]() | DynamicInvoke | Dynamically invokes (late-bound) the method represented by the current delegate. (Inherited from Delegate.) |
![]() | DynamicInvokeImpl | Dynamically invokes (late-bound) the method represented by the current delegate. (Inherited from Delegate.) |
![]() ![]() ![]() | Equals | Determines whether this multicast delegate and the specified object are equal. (Overrides Delegate::Equals(Object).) |
![]() ![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) In XNA Framework, this member is overridden by Finalize(). |
![]() ![]() ![]() | GetHashCode | Returns the hash code for this instance. (Overrides Delegate::GetHashCode().) |
![]() ![]() ![]() | GetInvocationList | Returns the invocation list of this multicast delegate, in invocation order. (Overrides Delegate::GetInvocationList().) |
![]() | GetMethodImpl | Returns a static method represented by the current MulticastDelegate. (Overrides Delegate::GetMethodImpl().) |
![]() | GetObjectData | Populates a SerializationInfo object with all the data needed to serialize this instance. (Overrides Delegate::GetObjectData(SerializationInfo, StreamingContext).) |
![]() ![]() ![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() ![]() ![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() ![]() | RemoveImpl | Removes an element from the invocation list of this MulticastDelegate that is equal to the specified delegate. (Overrides Delegate::RemoveImpl(Delegate).) |
![]() ![]() ![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
| Name | Description | |
|---|---|---|
![]() ![]() ![]() ![]() | Equality | Determines whether two MulticastDelegate objects are equal. |
![]() ![]() ![]() ![]() | Inequality | Determines whether two MulticastDelegate objects are not equal. |
MulticastDelegate is a special class. Compilers and other tools can derive from this class, but you cannot derive from it explicitly. The same is true of the Delegate class.
In addition to the methods that delegate types inherit from MulticastDelegate, the common language runtime provides two special methods: BeginInvoke and EndInvoke. For more information about these methods, see Calling Synchronous Methods Asynchronously.
A MulticastDelegate has a linked list of delegates, called an invocation list, consisting of one or more elements. When a multicast delegate is invoked, the delegates in the invocation list are called synchronously in the order in which they appear. If an error occurs during execution of the list then an exception is thrown.
The following example demonstrates the use of a class that is derived from MulticastDelegate.
using namespace System; // This class contains strings. It has a member method that // accepts a multicast delegate as a parameter and calls it. ref class HoldsStrings { public: // The following line causes the compiler to generate // a new delegate class named CheckAndPrintDelegate that // inherits from System.MulticastDelegate. delegate void CheckAndPrintDelegate( String^ str ); private: // An ArrayList that holds strings System::Collections::ArrayList^ myStringArray; public: HoldsStrings() { myStringArray = gcnew System::Collections::ArrayList; } // A method that adds more strings to the Collection void addstring( String^ str ) { myStringArray->Add( str ); } // Iterate through the strings and invoke the method(s) that the delegate points to void PrintAllQualified( CheckAndPrintDelegate^ myDelegate ) { System::Collections::IEnumerator^ myEnum = myStringArray->GetEnumerator(); while ( myEnum->MoveNext() ) { String^ str = safe_cast<String^>(myEnum->Current); myDelegate( str ); } } }; //end of class HoldsStrings // This class contains a few sample methods ref class StringFuncs { public: // This method prints a String* that it is passed if the String* starts with a vowel static void ConStart( String^ str ) { if ( !(str[ 0 ] == 'a' || str[ 0 ] == 'e' || str[ 0 ] == 'i' || str[ 0 ] == 'o' || str[ 0 ] == 'u') ) Console::WriteLine( str ); } // This method prints a String* that it is passed if the String* starts with a consonant static void VowelStart( String^ str ) { if ( (str[ 0 ] == 'a' || str[ 0 ] == 'e' || str[ 0 ] == 'i' || str[ 0 ] == 'o' || str[ 0 ] == 'u') ) Console::WriteLine( str ); } }; // This function demonstrates using Delegates, including using the Remove and // Combine methods to create and modify delegate combinations. int main() { // Declare the HoldsStrings class and add some strings HoldsStrings^ myHoldsStrings = gcnew HoldsStrings; myHoldsStrings->addstring( "This" ); myHoldsStrings->addstring( "is" ); myHoldsStrings->addstring( "a" ); myHoldsStrings->addstring( "multicast" ); myHoldsStrings->addstring( "delegate" ); myHoldsStrings->addstring( "example" ); // Create two delegates individually using different methods HoldsStrings::CheckAndPrintDelegate^ ConStartDel = gcnew HoldsStrings::CheckAndPrintDelegate( StringFuncs::ConStart ); HoldsStrings::CheckAndPrintDelegate^ VowStartDel = gcnew HoldsStrings::CheckAndPrintDelegate( StringFuncs::VowelStart ); // Demonstrate that MulticastDelegates may store only one delegate array<Delegate^>^DelegateList; // Returns an array of all delegates stored in the linked list of the // MulticastDelegate. In these cases the lists will hold only one (Multicast) delegate DelegateList = ConStartDel->GetInvocationList(); Console::WriteLine( "ConStartDel contains {0} delegate(s).", DelegateList->Length ); DelegateList = VowStartDel->GetInvocationList(); Console::WriteLine( "ConStartVow contains {0} delegate(s).", DelegateList->Length ); // Determine whether the delegates are System::Multicast delegates if ( dynamic_cast<System::MulticastDelegate^>(ConStartDel) && dynamic_cast<System::MulticastDelegate^>(VowStartDel) ) { Console::WriteLine( "ConStartDel and ConStartVow are System::MulticastDelegates" ); } // Run the two single delegates one after the other Console::WriteLine( "Running ConStartDel delegate:" ); myHoldsStrings->PrintAllQualified( ConStartDel ); Console::WriteLine( "Running VowStartDel delegate:" ); myHoldsStrings->PrintAllQualified( VowStartDel ); // Create a new, empty MulticastDelegate HoldsStrings::CheckAndPrintDelegate^ MultiDel; // Delegate::Combine receives an unspecified number of MulticastDelegates as parameters MultiDel = dynamic_cast<HoldsStrings::CheckAndPrintDelegate^>(Delegate::Combine( ConStartDel, VowStartDel )); // How many delegates is this delegate holding? DelegateList = MultiDel->GetInvocationList(); Console::WriteLine( "\nMulitDel contains {0} delegates.", DelegateList->Length ); // What happens when this mulitcast delegate is passed to PrintAllQualified Console::WriteLine( "Running the multiple delegate that combined the first two" ); myHoldsStrings->PrintAllQualified( MultiDel ); // The Remove and Combine methods modify the multiple delegate MultiDel = dynamic_cast<HoldsStrings::CheckAndPrintDelegate^>(Delegate::Remove( MultiDel, VowStartDel )); MultiDel = dynamic_cast<HoldsStrings::CheckAndPrintDelegate^>(Delegate::Combine( MultiDel, ConStartDel )); // Finally, pass the combined delegates to PrintAllQualified again Console::WriteLine( "\nRunning the multiple delegate that contains two copies of ConStartDel:" ); myHoldsStrings->PrintAllQualified( MultiDel ); } //end of main
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.






