Delegates
- A delegate is a method with a parameter and a return type.
- A delegate is a type that safely encapsulates a method.
- Delegates are object-oriented, type safe, and secure.
Special Notes
We can’t derive a custom class from the delegates because it is sealed.
[C# Code snippet]
public class MethodClass
{
public void Method1(string message)
{
System.Console.WriteLine("Method1 " + message);
}
public void Method2(string message)
{
System.Console.WriteLine("Method2 " + message);
}
}
class Program
{
public delegate void Del(string message);
static void Main(string[] args)
{
Del handler = DelegateMethod;
Console.WriteLine("calling a delegate method from current class");
// Call the delegate.
handler("Hello World");
Console.ReadLine();
MethodClass obj = new MethodClass();
Del d1 = obj.Method1;
Del d2 = obj.Method2;
Del d3 = DelegateMethod;
Del allMethodsDelegate = d1 + d2;
Console.WriteLine("calling a combined delegate method from other class");
allMethodsDelegate("Hello World");
allMethodsDelegate += d3;
Console.ReadLine();
Console.WriteLine("calling a combined delegate method from other class and current class");
allMethodsDelegate("Hello World");
Console.ReadLine();
int invocationCount = allMethodsDelegate.GetInvocationList().GetLength(0);
Console.WriteLine("Getting total count invocation list form a delegate, for the last one " + invocationCount.ToString() + " items (two form other class and one from current class ");
Console.ReadLine();
}
public static void DelegateMethod(string message)
{
Console.WriteLine(message);
}
public void MethodWithCallback(int param1, int param2, Del callback)
{
callback("The number is: " + (param1 + param2).ToString());
}
}
Vasanth KrishnanPosted Sep 1, 2014, 5:40 AM
It is nice one. But u have used one method with the name "MethodWithCallback" but u have not used anywhere else...