Question

I have simple WPF application where I using threads. E.g. In new thread I get DateTime and I want return it to the TextBox in main thread. I read to do this I must use ControlDispatcher.Invoke method. But something is wrong..

namespace Bizantyjskie
{
    public static class ControlExtensions
    {

        public static void InvokeIfRequired(this Control control, Action action)
        {
            if (System.Threading.Thread.CurrentThread != control.Dispatcher.Thread)
                control.Dispatcher.Invoke(action);
            else
                action();
        }
        public static void InvokeIfRequired<T>(this Control control, Action<T> action, T parameter)
        {
            if (System.Threading.Thread.CurrentThread != control.Dispatcher.Thread)
                control.Dispatcher.Invoke(action, parameter);
            else
                action(parameter);
        }
    }

    class watki
    {
        public watki(MainWindow mw)
        {
            _mw = mw;
        }
        public MainWindow _mw;

        public void dzialaj()
        {
            Thread watek1 = new Thread(new ThreadStart(w1));
            watek1.Start();
        }

        private void w1()
        {

            string godz = DateTime.Now.TimeOfDay.ToString();
            ControlExtensions.InvokeIfRequired((value) => _mw.tb_w1.Text = value, godz);
        }
      }
     }

Problem is with

ControlExtensions.InvokeIfRequired((value) => _mw.tb_w1.Text = value,
godz);

I got an error.

Cannot convert lambda expression to type
‘System.Windows.Controls.Control’ because it is not a delegate type

Answer 1

You’re calling an extension method as a static one and forgetting to pass a parameter. Change it to this:

_mw.InvokeIfRequired(value => _mw.tb_w1.Text = value, godz);

Alternatively, if you still want to call it as a static method:

ControlExtensions.InvokeIfRequired(_mw, 
    value => _mw.tb_w1.Text = value, godz);