Color different parts of a RichTextBox string

Question

I\'m trying to color parts of a string to be appended to a RichTextBox. I have a string built from different strings.

string temp = \"[\" + DateTime.Now.ToSh         


        

Answer 1

private void Log(string s , Color? c = null)
        {
            richTextBox.SelectionStart = richTextBox.TextLength;
            richTextBox.SelectionLength = 0;
            richTextBox.SelectionColor = c ?? Color.Black;
            richTextBox.AppendText((richTextBox.Lines.Count() == 0 ? "" : Environment.NewLine) + DateTime.Now + "\t" + s);
            richTextBox.SelectionColor = Color.Black;

        }

Answer 2

Using Selection in WPF, aggregating from several other answers, no other code is required (except Severity enum and GetSeverityColor function)

 public void Log(string msg, Severity severity = Severity.Info)
    {
        string ts = "[" + DateTime.Now.ToString("HH:mm:ss") + "] ";
        string msg2 = ts + msg + "\n";
        richTextBox.AppendText(msg2);

        if (severity > Severity.Info)
        {
            int nlcount = msg2.ToCharArray().Count(a => a == '\n');
            int len = msg2.Length + 3 * (nlcount)+2; //newlines are longer, this formula works fine
            TextPointer myTextPointer1 = richTextBox.Document.ContentEnd.GetPositionAtOffset(-len);
            TextPointer myTextPointer2 = richTextBox.Document.ContentEnd.GetPositionAtOffset(-1);

            richTextBox.Selection.Select(myTextPointer1,myTextPointer2);
            SolidColorBrush scb = new SolidColorBrush(GetSeverityColor(severity));
            richTextBox.Selection.ApplyPropertyValue(TextElement.BackgroundProperty, scb);

        }

        richTextBox.ScrollToEnd();
    }

Answer 3

This is the modified version that I put in my code (I'm using .Net 4.5) but I think it should work on 4.0 too.

public void AppendText(string text, Color color, bool addNewLine = false)
{
        box.SuspendLayout();
        box.SelectionColor = color;
        box.AppendText(addNewLine
            ? $"{text}{Environment.NewLine}"
            : text);
        box.ScrollToCaret();
        box.ResumeLayout();
}

Differences with original one:

• possibility to add text to a new line or simply append it
• no need to change selection, it works the same
• inserted ScrollToCaret to force autoscroll
• added suspend/resume layout calls