MulticastDelegate Class
Represents a multicast delegate; that is, a delegate that can have more than one element in its invocation list.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
The MulticastDelegate type exposes the following members.
| Name | Description | |
|---|---|---|
![]() ![]() ![]() | 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.) |
![]() ![]() ![]() | 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 the Object is reclaimed by garbage collection. (Inherited from Object.) In Silverlight for Windows Phone, this member is overridden by Finalize(). 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().) |
![]() ![]() ![]() | 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 Silverlight, using delegates to make asynchronous method calls is not supported. Calling BeginInvoke causes a NotSupportedException.
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 the MulticastDelegate class.
Note: |
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To run this example, see Building Examples That Use a Demo Method and a TextBlock Control. |
using System; // Declare a delegate class named CheckAndPrintDelegate that takes a // string. All delegates derive from System.MulticastDelegate. public delegate void CheckAndPrintDelegate(string str); // This class demonstrates using Delegates, including using the Remove and // Combine methods to create and modify delegate combinations. // class Example { private static System.Windows.Controls.TextBlock outputBlock; // A List that holds strings. private static System.Collections.Generic.List<string> strList = new System.Collections.Generic.List<string>(); // Iterate through the strings and invoke the method(s) that the delegate // represents. public static void PrintAllQualified(CheckAndPrintDelegate myDelegate) { foreach (string str in strList) { myDelegate(str); } } // This method prints the string that is passed to it if the string // starts with a consonant. public static void ConStart(string str) { if ("aeiou".IndexOf(str[0]) < 0) outputBlock.Text += str + "\n"; } // This method prints the string that is passed to it if the string // starts with a vowel. public static void VowelStart(string str) { if ("aeiou".IndexOf(str[0]) > -1) outputBlock.Text += str + "\n"; } public static void Demo(System.Windows.Controls.TextBlock outputBlock) { Example.outputBlock = outputBlock; strList.Add("this"); strList.Add("is"); strList.Add("a"); strList.Add("multicast"); strList.Add("delegate"); strList.Add("example"); // Create two delegates individually. CheckAndPrintDelegate ConStartDel = new CheckAndPrintDelegate(Example.ConStart); CheckAndPrintDelegate VowStartDel = new CheckAndPrintDelegate(Example.VowelStart); // GetInvocationList() returns an array of all delegates stored in the // linked list of the MulticastDelegate. In these cases the lists will // hold only one delegate. outputBlock.Text += "ConStartDel contains " + ConStartDel.GetInvocationList().Length + " delegate(s)." + "\n"; outputBlock.Text += "VowStartDel contains " + VowStartDel.GetInvocationList().Length + " delegate(s)." + "\n"; // Determine whether the delegates are System.Multicast delegates if (ConStartDel is System.MulticastDelegate && VowStartDel is System.MulticastDelegate) { outputBlock.Text += "ConStartDel and VowStartDel are System.MulticastDelegate." + "\n"; } // Run the two single delegates one after the other. outputBlock.Text += "Using ConStartDel delegate:\n"; PrintAllQualified(ConStartDel); outputBlock.Text += "\nUsing VowStartDel delegate:\n"; PrintAllQualified(VowStartDel); // Delegate.Combine receives a list of MulticastDelegates as parameters // and combines their invocation lists in a new Multicast delegate. CheckAndPrintDelegate MultiDel = (CheckAndPrintDelegate)Delegate.Combine(ConStartDel, VowStartDel); // How many delegates is this delegate holding? outputBlock.Text += "\nMultiDel contains " + MultiDel.GetInvocationList().Length + " delegates." + "\n"; // What happens when this mulitcast delegate is passed to // PrintAllQualified? outputBlock.Text += "Using the Multicast delegate that combines ConStartDel and VowStartDel:" + "\n"; PrintAllQualified(MultiDel); // The Remove and Combine methods create new Multicast delegates with // the specified delegates removed from or combined with the existing // invocation list. MultiDel = (CheckAndPrintDelegate)Delegate.Remove(MultiDel, VowStartDel); MultiDel = (CheckAndPrintDelegate)Delegate.Combine(MultiDel, ConStartDel); // Pass the new Multicast delegate to PrintAllQualified. outputBlock.Text += "\nUsing the Multicast delegate that contains two copies of ConStartDel:" + "\n"; PrintAllQualified(MultiDel); } } /* This example produces the following output: ConStartDel contains 1 delegate(s). VowStartDel contains 1 delegate(s). ConStartDel and VowStartDel are System.MulticastDelegate. Using ConStartDel delegate: this multicast delegate Using VowStartDel delegate: is a example Using the Multicast delegate that combines ConStartDel and VowStartDel: this is a multicast delegate example Using the Multicast delegate that contains two copies of ConStartDel: this this multicast multicast delegate delegate */
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.







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