c# - Highlighting a line in a RichTextBox1, line number = a variable

Question

I have a variable, lets say it = 5, and then I would like the line number 5 to be highlighted "blue" in my RichTextBox1. is that possible at all?

Or should I use something like a ListBox, DataGridView etc.

Answer 1

This will highlight the text in a given line in a RichTextBox if WordWrap is off:

void highLightALine(RichTextBox rtb, int line, Color hiLight)
{
    int i1 = rtb.GetFirstCharIndexFromLine(line);
    int i2 = rtb.GetFirstCharIndexFromLine(line + 1);
    if (i2 < 0) i2 = rtb.Text.Length;

    rtb.SelectionStart = i1;
    rtb.SelectionLength = i2 - i1;
    rtb.SelectionBackColor = hiLight;
}

Note that if WordWrap is true it will still highlight the line but only as far as it is visible. Its continuation on the next line will not be changed.

Also note that only Text can be highlighted. Trailing empty space can't be highlighted afaik. Here is an example of trying to owner-draw an RTB subclass..