Line information/number from Textbox in Silverlight

Question

Hi

Area : Textbox in Silverlight

Question: I need to know what "line number" that is currently edited.

I've tried: As a workaround I've tried splitting with textBox.Split("\r") and counting matches on Regex with similar performance. Performance during the first 2000 lines are acceptable but then it gets to slow.

Why: I have a Textbox and a Listbox side-by-side. The item index in the listbox corresponds to line number in the textbox and the content (of the ListboxItem) is a "processed" version of the corresponding line in textbox.

Alternative: A more performance friendly strategy than my hacks.

Answer 1

As I see it, you don't really need to use string.Split or Regex. Just iterate over the string and count '\r's up to the caret position.

var s = ...the string...
var r = 0;
var c = ...caret position...

for (var i = 0; i < c; i++)
  if (s[i] == '\r')
    r++;

This way, you'll find the line number without creating lots and lots of objects in memory...