Using lock on the key of a Dictionary

Question

I have a Dictionary.

EDIT: It was pointed out to me, that my example was bad. My whole intention was not to update the references

Answer 1

In your example, you can not do what you want to do!

You will get a System.InvalidOperationException with a message of Collection was modified; enumeration operation may not execute.

Here is an example to prove:

using System.Collections.Generic;
using System;

public class Test
{
    private Int32 age = 42;

    static public void Main()
    {
       (new Test()).TestMethod();
    }

    public void TestMethod()
    {
        Dictionary myDict = new Dictionary();

        myDict[age] = age.ToString();

        foreach(KeyValuePair pair in myDict)
        {
            Console.WriteLine("{0} : {1}", pair.Key, pair.Value);
            ++age;
            Console.WriteLine("{0} : {1}", pair.Key, pair.Value);
            myDict[pair.Key] = "new";
            Console.WriteLine("Changed!");
        }
    }   
}

The output would be:

42 : 42
42 : 42

Unhandled Exception: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Enumerator.MoveNext()
   at Test.TestMethod()
   at Test.Main()