#1,187 – Using a Lambda Expression When Adding to an Invocation List

Recall that an instance of a delegate can refer to more than one method (delegates are multicast).  You can use anonymous methods to declare a new instance of a delegate or to add methods to a delegate’s invocation list.

Since lambda expressions supersede anonymous methods, you can also use lambdas to initialize a delegate or to add to its invocation list.

        private delegate void StringHandlerDelegate(string s);

        static void Main(string[] args)
        {
            // Declare new delegate instance, with lambda
            // as its invocation list
            StringHandlerDelegate del1 = 
                (s) => Console.WriteLine(s);

            // Now add a 2nd method to delegate, also using
            // lambda expression
            del1 +=
                (s) => Console.WriteLine(new string(s.Reverse().ToArray())); 

            // When we invoke the delegate, both lambdas
            // are invoked
            del1("Mairzy Doats and Dozy Doats");

            Console.ReadLine();
        }

1187-001

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About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

3 Responses to #1,187 – Using a Lambda Expression When Adding to an Invocation List

  1. Pingback: Dew Drop – September 22, 2014 (#1860) | Morning Dew

  2. Gregory Shields says:

    Cool. Of course, you can also just use Action and not have to declare your own delegate.

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