C# - delegate(委派)

delegate類似於C語言的Function Pointer，允許定義參考物件來動態指向實體Method，並以呼叫此參考來執行特定實體Method，後來也延伸出匿名委派的功能，實體Method不需事先定義，而動態指定delegate運作邏輯。 

定義delegate參考物件，需與預定指向之實體Method有相同的Input/Output參數型別：

public delegate void ShowMessage(string);

定義n個相同Input/Output參數的實體Method，提供delegate指派：

public void Alert(string message){
    this.ClientScript.RegisterClientScriptBlock(
        this.GetType(),"alert","alert('"+message+"');",true);
}

public void Confirm(string message){
    this.ClientScript.RegisterClientScriptBlock(
        this.GetType(),"confirm","confirm('"+message+"');",true);
}

public void CustomMessage(string message){
    this.ClientScript.RegisterClientScriptBlock(
        this.GetType(),"customMessage","customMessage('"+message+"');",true);
}

指向實體Method&執行：

ShowMessage FunctionRef=new ShowMessage(Confirm);
FunctionRef("Alert Message");

FunctionRef=new ShowMessage(Alert);
FunctionRef("Confirm Message");

FunctionRef=new ShowMessage(CustomMessage);
FuncttionRef("CustomMessage Message");

匿名委派，不再事先定義實體Method，於Delegate宣告同時，指定參考Method的邏輯：

ShowMessage FunctionRef=delegate(string message){
    this.ClientScript.RegisterClientScriptBlock(
        this.GetType(),"alert","alert('"+message+"');",true);
};
FunctionRef("Alert Message");

ShowMessage FunctionRef=delegate(string message){
    this.ClientScript.RegisterClientScriptBlock(
        this.GetType(),"confirm","confirm('"+message+"');",true);
};
FunctionRef("Confirm Message");

ShowMessage FunctionRef=delegate(string message){
    this.ClientScript.RegisterClientScriptBlock(
        this.GetType(),"customMessage","customMessage('"+message+"');",true);
};
FunctionRef("CustomMessage Message");

出處