Question

I’m trying to create a form that will animate something while processing a particular task (passed as a delegate to the constructor). It’s working fine, but the problem I’m having is that I can’t instantiate a copy of my generic class if the particular method that I want to perform has a return type of void.

I understand that this is by design and all, but I’m wondering if there is a known workaround for situations like this.

If it helps at all my windows form looks like so (trimmed for brevity):

public partial class operatingWindow<T> : Form {     public delegate T Operation();     private Operation m_Operation;      private T m_ReturnValue;     public T ValueReturned { get { return m_ReturnValue; } }      public operatingWindow(Operation operation) { /*...*/ } } 

And I call it like:

operatingWindow<int> processing = new operatingWindow<int>(new operatingWindow<int>.Operation(this.doStuff)); processing.ShowDialog();  // ...  private int doStuff() {     Thread.Sleep(3000);      return 0; } 

Answer 1

I would rethink your design slightly.

If you implemented the processing in a base class, you could subclass it with 2 alternatives that would be nearly interchangable.

The first could be like yours, where it takes an Operation that returns a value. (I would rework this to use Func<T> instead of having your own delegate type, though.

The second could just take a simple Action and not provide a return value. Both could use the same animation/display/etc. routines, but provide a different way of working. You could also pass this off to other methods using the base class, which would provide a lot of flexibility.

With this approach, you could call this like:

private void DoSleep() {     Thread.CurrentThread.Sleep(5000); } private int ReturnSleep() {     Thread.CurrentThread.Sleep(5000);     return 5000; } ... {     var actionWindow = new OperatingWindowAction(this.DoSleep);     actionWindow.Execute();     var funcWindow = new OperatingWindowFunc<int>(this.ReturnSleep);     funcWindow.Execute();     int result = funcWindow.Result; } 

This would look something like:

public abstract partial class OperatingWindowBase : Form {     public void Execute()     {         // call this.OnExecute(); asyncronously so you can animate     }     protected abstract void OnExecute(); }  public class OperatingWindowFunc<T> : OperatingWindowBase {     Func<T> operation;     public T Result { get; private set; }     public OperatingWindowFunc<T>(Func<T> operation)     {         this.operation = operation;     }     protected override OnExecute()     {         this.Result = operation();     } }  public class OperatingWindowAction {     Action operation;     public OperatingWindow(Action operation)     {         this.operation = operation;     }     protected override OnExecute()     {         operation();     } }