WPF scroll multiline textbox to caret position - wpf

Question

today I'm searching for a way to scroll a multiline, dynamically sized textbox.
I want to scroll to the Caret and don't find any helpful informations at the internet.
After trying many things i know how to scroll to the end of a line, but not how to scroll to the caret.
The scroll to the right line is already implemented, but the horizontal scroll part is already missing.
private void txtText_PreviewKeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Down || e.Key == Key.Up)
{
var CurrentLineIndex = txtText.GetLineIndexFromCharacterIndex(((TextBox)sender).SelectionStart);
txtText.ScrollToLine(CurrentLineIndex);
}
}
This is my current code, which does scrolling to the right line for me.
Tryed to do something simular for the horizontal scrolling:
var rect = ((TextBox)sender).GetRectFromCharacterIndex(((TextBox)sender).CaretIndex);
txtText.ScrollToHorizontalOffset(Math.Max((txtText.HorizontalOffset + rect.Right - (txtText.ActualWidth - 40)), 0.0));
But it doesn't work like expected, it scrolls not to the horizontal caret position.
Think, i had to discribe it better:
if i move the caret with the left or right arrow, it will work fine without implementing anything.
It doesn't work if i do this:
Move from one line to another.
Sometimes one of these lines is longer or shorter than another and at this case i had to scroll to the caret position.
Example:
Line1 is longer than line2
I navigate with the key "end" at the keyboard to the end of line1.
Then i navigate to to line2.
It all works correctly, the caret jumps to the end of line2 and it will scrolls automatically into visibile area.
But if i go back from line2 to line1 the caret is position right at the end of line1. But it scrolls not to the end of line1.

Answer 1

the problem was that i used a Style template and forgot a necessary thing:
to pass
ContentTemplate="{TemplateBinding ContentTemplate}" CanContentScroll="{TemplateBinding CanContentScroll}"
to the ScrollContentPresenter.
After doing this, the standard behaviour will work well!