TextBox_TextChanged

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
TextBox textBox = sender as TextBox;
TextChange[] change = new TextChange[e.Changes.Count];
e.Changes.CopyTo(change, 0);
int offset = change[0].Offset;
if (change[0].AddedLength > 0)
{
double num = 0;
if (!Double.TryParse(textBox.Text, out num))
{
textBox.Text = textBox.Text.Remove(offset, change[0].AddedLength);
textBox.Select(offset, 0);
}
}
}