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Control.Invoke with input Parameters

Asked 2009-04-23T23:10:22.037
13

From what I've found in C#, the Control.Invoke method requires that you use a delegate with no input parameters. Is there any way around this? I would like to invoke a method to update the UI from another thread and pass to string parameters to it.

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4 Answers

23

Which version of C# are you using? If you are using C#3.5 you can use closures to avoid passing in parameters.

With C#3.5
public static class ControlExtensions
{
  public static TResult InvokeEx<TControl, TResult>(this TControl control,
                                             Func<TControl, TResult> func)
    where TControl : Control
  {
    return control.InvokeRequired
            ? (TResult)control.Invoke(func, control)
            : func(control);
  }

  public static void InvokeEx<TControl>(this TControl control,
                                        Action<TControl> func)
    where TControl : Control
  {
    control.InvokeEx(c => { func(c); return c; });
  }

  public static void InvokeEx<TControl>(this TControl control, Action action)
    where TControl : Control
  {
    control.InvokeEx(c => action());
  }
}

Safely invoking code now becomes trivial.

this.InvokeEx(f => f.label1.Text = "Hello World");
this.InvokeEx(f => this.label1.Text = GetLabelText("HELLO_WORLD", var1));
this.InvokeEx(() => this.label1.Text = DateTime.Now.ToString());

With C#2.0 it becomes less trivial
public class MyForm : Form
{
  private delegate void UpdateControlTextCallback(Control control, string text);
  public void UpdateControlText(Control control, string text)
  {
    if (control.InvokeRequired)
    {
      control.Invoke(new UpdateControlTextCallback(UpdateControlText), control, text);
    }
    else
    {
      control.Text = text;
    }
  }
}

Using it simple, but you have to define more callbacks for more parameters.

this.UpdateControlText(label1, "Hello world");
answered 2009-04-23T23:30:00.977
6

As Luke says, use Control.Invoke like this...

For example in a form:

public delegate void DelegatePassMessages(string name, int value);

public DelegatePassMessages passMessage;

In the contructor:

passMessage = new DelegatePassMessages (this.MessagesIn);

Then the MessagesIn function to receive data:

public void MessagesIn(string name, int value)
{

}

Then to pass data to your form:

formName.Invoke(formName.passMessage, new Object[] { param1, param2});
answered 2009-06-04T12:31:44.310
1

Here ya go using lambda expressions with the Invoke() extension + an input parameter.

Using: action(STARS db)

_ccb.GetImagerFRU_PartNbr().Invoke(new Action<STARS>(dbase => _ccb.GetImagerFRU_PartNbr().Text = dbase.PartNumber(serial) ?? String.Empty), db);
answered 2013-06-08T07:28:29.217
0

Found an elegant method for .net 2.0 with anonymous methods wrapped in a MethodInvoker Delegate. That way is no need to define own delegates all the time. Example:

    private void InitUI(Guid id, string typename)
    {
        MethodInvoker inv = delegate{tvMatrix.Nodes[0].Nodes.Add(id.ToString(), typename);};
        tvMatrix.Invoke(inv);
    }
answered 2010-12-23T07:36:28.063

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