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c#scopeanonymous-methods

Scope of variables inside anonymous functions in C#


I have a doubt in scope of varibles inside anonymous functions in C#.

Consider the program below:

 delegate void OtherDel(int x);

        public static void Main()
        {
            OtherDel del2;
            {
                int y = 4;
                del2 = delegate
                {
                      Console.WriteLine("{0}", y);//Is y out of scope
                };
            }

           del2();
        }

My VS2008 IDE gives the following errors: [Practice is a class inside namespace Practice]

1.error CS1643: Not all code paths return a value in anonymous method of type 'Practice.Practice.OtherDel' 2.error CS1593: Delegate 'OtherDel' does not take '0' arguments.

It is told in a book: Illustrated C# 2008(Page 373) that the int variable y is inside the scope of del2 definition. Then why these errors.


Solution

  • Two problem;

    1. you aren't passing anything into your del2() invoke, but it (OtherDel) takes an integer that you don't use - you still need to supply it, though (anonymous methods silently let you not declare the params if you don't use them - they still exist, though - your method is essentially the same as del2 = delegate(int notUsed) {...})
    2. the delegate (OtherDel) must return an int - your method doesn't

    The scoping is fine.