C# – How to add bold text to rich text box

cwinforms

I'm working with Visual Studio Express 2012 with C#.

I am using code to add text to a RichTextBox. Each time there are 2 lines added. The first line needs to be bold and the second line normal.

Here is the only thing I could think to try, even though I was sure it would not work:

this.notes_pnl.Font = new Font(this.notes_pnl.Font, FontStyle.Bold);
this.notes_pnl.Text += tn.date.ToString("MM/dd/yy H:mm:ss")  + Environment.NewLine;
this.notes_pnl.Font = new Font(this.notes_pnl.Font, FontStyle.Regular);
this.notes_pnl.Text += tn.text + Environment.NewLine + Environment.NewLine;

How can I add bolded lines to a rich text box?

Thanks for the answers submitted so far. I think I need to clarify a little.
I am not adding these 2 lines 1 time. I will be adding the lines several times.

Best Answer

In order to make the text bold you just need to surround the text with \b and use the Rtf member.

this.notes_pln.Rtf = @"{\rtf1\ansi this word is \b bold \b0 }";

OP mentioned that they will be adding lines over time. If that is the case then this could be abstracted away into a class 

class RtfBuilder { 
  StringBuilder _builder = new StringBuilder();

  public void AppendBold(string text) { 
    _builder.Append(@"\b ");
    _builder.Append(text);
    _builder.Append(@"\b0 ");
  }

  public void Append(string text) { 
    _builder.Append(text);
  }

  public void AppendLine(string text) { 
    _builder.Append(text);
    _builder.Append(@"\line");
  }

  public string ToRtf() { 
    return @"{\rtf1\ansi " + _builder.ToString() + @" }";
  }
}
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