C#

• If you want to call the method normally (without canceling capabilities), just call it.
• If you want to call a method in a cancelable fashion, call object Controller.PerformOngoingOperation(method, string id, params object[] args); another thread can later call Controller.CancelOngoingOperation(string id).
  • PerformOngoingOperation checks that the method passed (more on that later) has the appropriate OngoingOperationAttribute; if so, it invokes it. It also stores in an internal dictionary a map from ids to boolean "should cancel now" variables.
  • The method in question finds its ID. This is kludgy... it involves reflections to find the calling method, check if the calling method is PerformOngoingOperation, and if so, ready the id parameter.
  • It then uses this id to performs a series of checks throughout its operation against that internal map from ids to "should cancel now"; if at any point the should-cancel bit is true, it finishes what it's doing and returns.
  • Then, PerformOngoingOperation will return the results of the method, whether canceled prematurely or not. So it acts just like invoking the method (good for users!), but can allow cancellation.
  • The should-cancel bit is set by Control.CancelOngoingOperation(string id), with consequences as above.

class C
{
    delegate int annoying(int param1, bool param2, string param3);
    void Method()
    {
        string id;
        int retVal = (int)Control.PerformOngoingOperation(new annoying(Library.Object.Method), out id, param1, param2, param3);
    }
}

int retVal;
string id = Control.PerformOngoingOperation((MethodInvoker)(new delegate() { retVal = Library.Object.Method(param1, param2, param3); }));

string id;
int retVal = Control.PerformOngoingOperation(Library.Object.Method, out id, param1, param2, param3);