Automating the InvokeRequired code pattern

Lee's approach can be simplified further

public static void InvokeIfRequired(this Control control, MethodInvoker action){    // See Update 2 for edits Mike de Klerk suggests to insert here.    if (control.InvokeRequired) {        control.Invoke(action);    } else {        action();    }}

And can be called like this

richEditControl1.InvokeIfRequired(() =>{    // Do anything you want with the control here    richEditControl1.RtfText = value;    RtfHelpers.AddMissingStyles(richEditControl1);});

There is no need to pass the control as parameter to the delegate. C# automatically creates a closure.

UPDATE:

According to several other posters Control can be generalized as ISynchronizeInvoke:

public static void InvokeIfRequired(this ISynchronizeInvoke obj,                                         MethodInvoker action){    if (obj.InvokeRequired) {        var args = new object[0];        obj.Invoke(action, args);    } else {        action();    }}

DonBoitnott pointed out that unlike Control the ISynchronizeInvoke interface requires an object array for the Invoke method as parameter list for the action.

UPDATE 2

Edits suggested by Mike de Klerk (see comment in 1st code snippet for insert point):

// When the form, thus the control, isn't visible yet, InvokeRequired  returns false,// resulting still in a cross-thread exception.while (!control.Visible){    System.Threading.Thread.Sleep(50);}

See ToolmakerSteve's comment below for concerns about this suggestion.

You could write an extension method:

public static void InvokeIfRequired(this Control c, Action<Control> action){    if(c.InvokeRequired)    {        c.Invoke(new Action(() => action(c)));    }    else    {        action(c);    }}

And use it like this:

object1.InvokeIfRequired(c => { c.Visible = true; });

EDIT: As Simpzon points out in the comments you could also change the signature to:

public static void InvokeIfRequired<T>(this T c, Action<T> action)     where T : Control

Here's the form I've been using in all my code.

private void DoGUISwitch(){     Invoke( ( MethodInvoker ) delegate {        object1.Visible = true;        object2.Visible = false;    });} 

I've based this on the blog entry here. I have not had this approach fail me, so I see no reason to complicate my code with a check of the InvokeRequired property.

Hope this helps.