C# - Anonymous Method

As the name suggests, an anonymous method is a method without a name. Anonymous methods in C# can be defined using the delegate keyword and can be assigned to a variable of delegate type.

Example: Anonymous Method

public delegate void Print(int value);

static void Main(string[] args)
{
    Print print = delegate(int val) { 
        Console.WriteLine("Inside Anonymous method. Value: {0}", val); 
    };

    print(100);
}

Try it

Output:

Inside Anonymous method. Value: 100

Anonymous methods can access variables defined in an outer function.

Example: Anonymous Method

public delegate void Print(int value);

static void Main(string[] args)
{
    int i = 10;
    
    Print prnt = delegate(int val) {
        val += i;
        Console.WriteLine("Anonymous method: {0}", val); 
    };

    prnt(100);
}

Try it

Output:

Anonymous method: 110

Anonymous methods can also be passed to a method that accepts the delegate as a parameter.

In the following example, PrintHelperMethod() takes the first parameters of the Print delegate:

Example: Anonymous Method as Parameter

public delegate void Print(int value);

class Program
{
    public static void PrintHelperMethod(Print printDel,int val)
    { 
        val += 10;
        printDel(val);
    }

    static void Main(string[] args)
    {
        PrintHelperMethod(delegate(int val) { Console.WriteLine("Anonymous method: {0}", val); }, 100);
    }
}

Try it

Output:

Anonymous method: 110

Anonymous methods can be used as event handlers:

Example: Anonymous Method as Event Handler

saveButton.Click += delegate(Object o, EventArgs e)
{ 
    System.Windows.Forms.MessageBox.Show("Save Successfully!"); 
};

C# 3.0 introduced the lambda expression which also works like an anonymous method.

Anonymous Method Limitations

It cannot contain jump statement like goto, break or continue.
It cannot access ref or out parameter of an outer method.
It cannot have or access unsafe code.
It cannot be used on the left side of the is operator.

Points to Remember :

Anonymous method can be defined using the delegate keyword
Anonymous method must be assigned to a delegate.
Anonymous method can access outer variables or functions.
Anonymous method can be passed as a parameter.
Anonymous method can be used as event handlers.