Task.Run and Func<>

Question

How can I run a Task that return value and takes a parameter? I see that there is an overloaded method Task.Run<TResult>(Func<TResult>) but how I can pass a parameter there?

Answer 1

Func<TResult> doesn't take a parameter. Typically you would capture the parameter using a lambda expression instead. For example:

public void DoSomething(string text)
{
    Task<int> task = Task.Run(() => text.Length);
    ...
}

Here text is a captured variable... so even though you're just creating a Func<int>, it's using the method parameter.

Answer 2

You could use the Task.Factory.StartNew() overloads to pass in a "state" object that holds all the parameters you want to you use. Here's a very basic example passing in a NameValueCollection, but you could obviously pass in any type of object you wanted.

Task<bool>.Factory.StartNew(
    ( a ) => {
        NameValueCollection nvc = a as NameValueCollection;
        if( nvc != null ) {
            nvc.AllKeys.ForEach( k => Console.WriteLine( nvc[k] ) );
        }
        return true;
    },
    new NameValueCollection() { { "param1", "hithere!" } } );