Given function:
private static int Add(int x, int y)
{
Console.WriteLine("Add() invoked on thread {0}.",
Thread.CurrentThread.ManagedThreadId);
Thread.Sleep(500);
return x + y;
}
I tried this:
Task<int> t = new Task<int>(x, y => Add(x, y), 5, 6); // 5+6
t.Start();
t.Wait();
// Get the result (the Result property internally calls Wait)
Console.WriteLine("The sum is: " + t.Result);
It cant be compiled, obviously. How do I do this correctly?
First, I'd use Task.Run instead of explicitly creating a new Task. Then I'd await the result rather than blocking until it is completed. This will require the enclosing method to be marked async - you can read more about async/await in this blog post. I'd suggest reading many more on that blog.
You can capture your arguments as part of the lambda expression. This part is the reason why your current code doesn't compile. This is generally more useful than the Action<object> overload in the Task constructor. The end result:
private static async Task AddAsync()
{
var result = await Task.Run(() => Add(5, 6));
Console.WriteLine("The sum is: {0}", result);
}
async to the enclosing method (as it suggests) in order to use await. You might want to read this blog post (and many more on that blog!). Task.Run is available in .NET 4.5 - what are you using?Result you're just blocking while you wait for the other thread which sort of renders it a bit pointless.Task<int> t = new Task<int>(x, y => Add(x, y), 5, 6); // 5+6
What are you trying to do is to define a Task that takes parameters, and passes these parameters to its inner code.
You can use the overload which takes an object parameter to pass values, like this:
Task<int>.Factory.StartNew(obj => {
var arr = obj as int[];
return arr[0] + arr[1];
}, new[] { 5, 4 });
(x, y) => Add(x, y)and two, there's no overload ofnew Task<T>that takes theFunc<int, int, int>you're trying to pass. That doesn't hurt, though - you can just capture the arguments directly -() => Add(5, 6). There really isn't much of a reason to pass the arguments in any other way...Task.Run(...)for long-running operations like disk- oder database-IO. See channel9.msdn.com/Series/Three-Essential-Tips-for-Async/… for a great overview.