How to solve "Cross thread operation not valid"

public delegate R InvokeAction<R>();
public delegate R InvokeParameterizedAction<R>(params object[] data);
 

public static void CrossThread<T>(this T t, InvokeAction action) where T : Control
        {
            if (t.InvokeRequired)
                t.Invoke(action);
            else
                action();
        }
public static R CrossThread<T, R>(this T t, InvokeParameterizedAction<R> action, params object[] data) where T : Control
        {
            if (t.InvokeRequired)
                return (R)t.Invoke(action, data);
            else
                return action(data);
        }

TextBoxObject.CrossThread(()=>
{
// ... Do stuff here from another thread
});
// OR

TextBoxObject.CrossThread((textbox,newtext) =>
{
textbox.Text = newtext;
}, TextBoxObject,"Update Text");

 Private Sub LastUpdate(ByVal sender As Object, ByVal e As PropertyChangedEventArgs)
        If Me.InvokeRequired Then
            Me.Invoke(New MethodInvoker(AddressOf LastUpdate))
        Else
            Me.textbox1.Text = e.PropertyName
....

    Private Sub UpdateLabel()
        Dim tmpMain As frmMain = Application.OpenForms.Item("frmMain")
        If tmpMain.InvokeRequired Then
            tmpMain.Invoke(New MethodInvoker(AddressOf UpdateLabel))
        Else
            tmpMain.lblUsersCon.Text = "blah de blah blah"
        End If
    End Sub