How to get the selected line in a Text Box?

Question

I have text box with text wrapping enabled in my Windows Phone 7 app, how do I get the line count at the character selected by the user? For example, if a text box it looked like this:

test
text
bo|x
is
here

, with "|" representing the selected character, the line count would be 3. I need to do this at any point in time, most specifically when the text is changed. I could count the number of newlines in a text box without text wrapping, but this is clearly a different scenario.

Answer 1

I figured this out myself:

Rect rec = textbox.GetRectFromCharacterIndex(textbox.SelectionStart);
double rectop = rec.Top;
double lineheight = text.LineHeight;
int result = (int)(rectop / lineheight + 1);

result = the selected line.

Answer 2

only a stupid way:

you can handle these event:ManipulationStarted ManipulationCompleted

From the callback args you can find the point(x,y) user point, maybe it is the coordinate of selected place.

and you know the height of everyline from the prop —— lineHeight

and do a division