Change color of text within a WinForms RichTextBox

Question

I have a RichTextBox that I write a string to every time I click a Form button. The string ends with a newline so each time I add a string, it appends to the bottom of the RichTextBox. Each string begins with the string "Long" or "Short" and ends with Environment.NewLine. 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? If you need further clarification of the question comment below.

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. Didn't try it out but that's how I remember it working.

Answer 2

I was just doing this in a program I was writing. I was doing something like itsmatt but I feel a bit simpler. You are able to just set the selectioncolor and from that point on the RichTextBox will be that color until you change it to something else. If you are testing every line this seems to work out well and is easy.

if(myString == "Long") 
{ 
richTextBox.SelectionColor = Color.Red; 
}
else
{
richTextBox.SelectionColor = Color.Green
}
richTextBox.AppendText(myString);