Why is my method not found by the compiler?

I have a class "Worker" with an entry method 

internal void Run()
{
//do stuff...
}

I have a subclass for testing ("TestWorker:Worker") with an entry method

internal void Run(object aParam)
{
//do something with aParam, then..
Run();
}

I have a test app which launches an instance of TestWorker in a new thread,

        Worker worker;
        Thread workerThread;
...
        worker = new TestWorker();
        workerThread = new Thread(new ParameterizedThreadStart(worker.Run));
        workerThread.Start("something");

This won't compile, and the compiler reports that the parameterized delegate (in my subclass) cannot be found. I can overcome the problem by declaring a dummy virtual Run(object) method in my Worker class such that my TestWorker.Run(object) overrides it but IMHO it is an inelegant solution, so why do I have to do this? Is it a compiler idiosyncrasy, or am I doing something logically incorrect?

Jon Skeet
people
quotationmark

The problem is that the compile-time type of worker is just Worker - and there isn't a Worker.Run method accepting a parameter.

This has nothing to do with delegates per se - you wouldn't be able to call

worker.Run("foo");

either. The simplest way to fix this is just to change the declaration of worker to be TestWorker. Alternatively, use a separate local variable:

TestWorker testWorker = new TestWorker();
workerThread = new Thread(new ParameterizedThreadStart(testWorker.Run));
worker = testWorker;

people

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