Question

I have a RichTextBox that I write a string to every time I click a Form button. Each string begins with the string “Long” or “Short” and ends with a newline. Each time I add a string, it appends to the bottom of the RichTextBox. I’d like to color each line red if it beings with “Long” and blue if it begins with “Short”. How can I do this?

Answer 1

Sure, so what you can do is use the SelectionStart, SelectionLength and SelectionColor properties to accomplish this. It works quite well.

Check out this page for info on these properties.

You can know the length of the RichTextBox text and color this as you go by setting the SelectionStart property to the current length, get the Length of the string you are going to append, set the SelectionLength and then set the SelectionColor as appropriate. Rinse and repeat for each string added.

int length = richTextBox.TextLength;  // at end of text
richTextBox.AppendText(mystring);
richTextBox.SelectionStart = length;
richTextBox.SelectionLength = mystring.Length;
richTextBox.SelectionColor = Color.Red;

Something like that. That’s how I remember it working.