Task with Action Delegate accepting string parameter

Question

I have just started with parallel programming. I want to create an action delegate method that print a message on console. When I chenge Action<string> to Action<object> and PritMessage parameter to to object its work but with 'string compiler throws an error.

The best overloaded method match for 'System.Threading.Tasks.Task.Task(System.Action, object)'.
Argument 1: cannot convert from 'System.Action<string>' to 'System.Action<object>'

static void Main(string[] args)
{
    string message = "test";
    Action<string> print = PrintMessage;
    Task task = new Task(print, message); 
    task.Start();
    Console.ReadKey();
}

static void PrintMessage(string message)
{
    Console.WriteLine(message);
}

Answer 1

If you examine the Task constructors, you'll see that you can't create a task with Action which accepts something other than no parameters or single object parameter.

For this particular sample you can simply run the Task with lambda, like this:

Task.Run(() =>
{
    PrintMessage(message);
}

However, better approach is to change signature and cast an in-parameter:

static void Main(string[] args)
{
    var message = "test";
    Task task = new Task(PrintMessage, message); 
    task.Start();
    Console.ReadKey();
}

static void PrintMessage(object messageObj)
{
    var message = messageObj as string;
    Console.WriteLine(message);
}

Or simply print the object in Console:

static void PrintMessage(object message)
{
    Console.WriteLine(message);
}