How can I select (with focus) the text in telerik:RadNumericUpDown - wpf

Question

This NumericUpDown (NUD) floats over a map. When it gets visible I need to re-direct the next key-stroke inside the control overriding the current value.
With great pain I've found this solution:
private void LengthInput_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
{
if ((bool)(e.NewValue))
{
...
LengthInputBox.ShowButtons = true;
try
{
LengthInputBox.Focus();
if (m_lengthTextBox == null)
{
LengthInputBox.ApplyTemplate();
m_lengthTextBox = LengthInputBox.Template.FindName("textbox", LengthInputBox) as TextBox;
}
if (m_lengthTextBox != null)
{
m_lengthTextBox.SelectAll();
m_lengthTextBox.Focus();
}
}
finally
{
LengthInputBox.ShowButtons = false;
}
...
NUD is the LengthInputBox control. Focus method sets the focus on the NUD buttons.
Template.FindName("textbox"... retrieve the internal TextBox of NUD. If found, or previously found, it selects all and set focus on the text.
Finally, I remove the Up/Down buttons (I don't need them. Although I've done lot of variations with or without them, their presence does not change the behavior...)
It works for the first time, but on the second attempt it fails again.
Any ideas?

Answer 1

Select and Focus are bit slow. Using a Dispatcher has solved the issue:
private void LengthInputBox_GotFocus(object sender, RoutedEventArgs e)
{
if (m_lengthTextBox == null)
{
LengthInputBox.ApplyTemplate();
m_lengthTextBox = LengthInputBox.Template.FindName("textbox", LengthInputBox) as TextBox;
}
if (m_lengthTextBox != null)
{
m_lengthTextBox.Focusable = true;
m_lengthTextBox.IsTabStop = true;
if (!m_lengthTextBox.IsFocused)
Dispatcher.BeginInvoke(new Action(() =>
{
var dot = m_lengthTextBox.Text.IndexOf('.');
m_lengthTextBox.Select(dot, m_lengthTextBox.Text.Length - dot);
m_lengthTextBox.Focus();
}));
}
LengthInputBox.CaptureMouse();
}
(Don't forget to release the mouse:
private void LengthInput_KeyDown(object sender, KeyEventArgs e)
{
switch (e.Key)
{
case Key.Escape:
case Key.Enter:
LengthInputBox.ReleaseMouseCapture();
ViewModel.IsLengthInputVisible = false;
e.Handled = true;
break;
}
}
)