Thank you for writing.
The observed behavior is the default behavior for the Controls in Windows Forms. It seems that the control is not yet fully initialized before it is made visible. I found similar thread on StackOverflow. There is a suggestion to call the internal CreateControl method of the control to force its initialization and this worked fine on my end.
Alternatively, you can select the desired page as you did. Here is the method:
method = control.GetType().GetMethod(
, BindingFlags.Instance | BindingFlags.NonPublic);
parameters = method.GetParameters();
Debug.Assert(parameters.Length == 1,
"Looking only for the method with a single parameter"
"Single parameter is not of type boolean"
I hope that you find this information useful.
All the best,
the Telerik team