Question - What is a multicast delegate in C#?
Answer -
A multicast delegate holds the references or addresses to more than one function at a single time. Whenever we invoke the multicast delegate, it will invoke all the other functions that are being referred by that multicast delegate. You should use the complete method signature the same as the delegate to call multiple methods. For example:
namespace MulticastDelegate
{
public class Rectangle
{
public void Area(double Width, double Height)
{
Console.WriteLine(@"Area is {0}", (Width * Height));
}
public void Perimeter(double Width, double Height)
{
Console.WriteLine(@"Perimeter is {0}", (2 * (Width + Height)));
}
static void Main(string[] args)
{
Rectangle rect = new Rectangle();
rect.Area(23.45, 67.89);
rect.Perimeter(23.45, 67.89);
Console.ReadKey();
}
}
}
Here, we created an instance of the Rectangle class and then called the two different methods. Now a single delegate will invoke these two methods Area and Perimeter. These defined methods are having the same signature as the defined delegates that hold the reference to these methods.
Creating multicast delegate:
namespace MulticastDelegateDemo
{
public delegate void RectangleDelete(double Width, double Height);
public class Rectangle
{
public void Area(double Width, double Height)
{
Console.WriteLine(@"Area is {0}", (Width * Height));
}
public void Perimeter(double Width, double Height)
{
Console.WriteLine(@"Perimeter is {0}", (2 * (Width + Height)));
}
static void Main(string[] args)
{
Rectangle rect = new Rectangle();
RectangleDelete rectDelegate = new RectangleDelete(rect.Area);
rectDelegate += rect.Perimeter;
rectDelegate(23.45, 67.89);
Console.WriteLine();
rectDelegate.Invoke(13.45, 76.89);
Console.WriteLine();
//Removing a method from delegate object
rectDelegate -= rect.Perimeter;
rectDelegate.Invoke(13.45, 76.89);
Console.ReadKey();
}
}
}