Task.ContinueWith method requires task argument?

Question

I have a class with two methods, Load() and Process(). I want to be able to run these individually as background tasks, or in sequence. I like the ContinueWith() syntax, but I'm not able to get it to work. I have to take a Task parameter on the method I continue with and cannot have a Task parameter on the initial method.

I would like to do it without lambda expressions, but am I stuck either using them, forcing a task parameter on one of the methods, or creating a third method LoadAndProcess()?

void Run()
{
    // doesn't work, but I'd like to do it
    //Task.Factory.StartNew(MethodNoArguments).ContinueWith(MethodNoArguments);

    Console.WriteLine("ContinueWith");
    Task.Factory.StartNew(MethodNoArguments).ContinueWith(MethodWithTaskArgument).Wait();

    Console.WriteLine("Lambda");
    Task.Factory.StartNew(() => { MethodNoArguments(); MethodNoArguments(); }).Wait();

    Console.WriteLine("ContinueWith Lambda");
    Task.Factory.StartNew(MethodNoArguments).ContinueWith(x => { 
            MethodNoArguments(); 
        }).Wait();
}

void MethodNoArguments()
{
    Console.WriteLine("MethodNoArguments()");
}

void MethodWithTaskArgument(Task t = null)
{
    Console.WriteLine("MethodWithTaskArgument()");
}

Answer 1

In all overloads of ContinueWith(), the first parameter is a delegate that takes a Task, so you can't pass a parameterless delegate to it.

I think that using lambdas is perfectly fine and that it doesn't hurt readability. And the lambda in your code is unnecessarily verbose:

Task.Factory.StartNew(MethodNoArguments).ContinueWith(_ => MethodNoArguments())

Or, as Cory Carson pointed out in a comment, you could write an extension method:

public static Task ContinueWith(this Task task, Action action)
{
    return task.ContinueWith(_ => action());
}