Line Numbering of RichTextBox in .NET 2.0

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Introduction

This article demonstrates how to add line numbers to a rich text box control. This is done by adding a picture box control on the left side of the rich text box control. When the appropriate events happen on the Form or on the RichTextBox control we call a method that paints the line numbers on the PictureBox control. This approach is more accurate and efficient than other approaches I've seen where another textbox control was used for printing the line numbers. The PictureBox will only print the line numbers that are currently visible in the RichTextBox control.
During the process of constructing this code sample, I initially based it on the code sample provided in the article http://www.codeproject.com/cs/miscctrl/numberedtextbox.asp and enhanced it by doing the following:

1. Replace the Label control for numbering with a PictureBox
2. I fixed the scrolling problem with that implementation due to the fact that RichTextBox uses smooth scrolling (scrolling with the scrollbar scrolls the text in pixels, not in lines), as a result sometimes the first line may be displayed in half, at which case the line numbering should address it.

Here is the code for printing the line numbers. Note that we have a RichTextBox control
called MyRichTextBox and a PictureBox control called MyPictureBox. The method gets one
argument which is the Graphics of the PictureBox control.
This is the method DrawRichTextBoxLineNumbers:

 Private Sub DrawRichTextBoxLineNumbers(ByRef g As Graphics)
  'Calculate font heigth as the difference in Y coordinate 
  'between line 2 and line 1
  'Note that the RichTextBox text must have at least two lines. 
  '  So the initial Text property of the RichTextBox 
  '  should not be an empty string. It could be something 
  '  like vbcrlf & vbcrlf & vbcrlf 
  With MyRichTextBox
   Dim font_height As Single 
   font_height = .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(2)).Y _
         - .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(1)).Y
   If font_height = 0 Then Exit Sub

   'Get the first line index and location
   Dim first_index As Integer
   Dim first_line As Integer
   Dim first_line_y As Integer
   first_index = .GetCharIndexFromPosition(New _
         Point(0, g.VisibleClipBounds.Y + font_height / 3))
   first_line = .GetLineFromCharIndex(first_index)
   first_line_y = .GetPositionFromCharIndex(first_index).Y

   'Print on the PictureBox the visible line numbers of the RichTextBox
   g.Clear(Control.DefaultBackColor)
   Dim i As Integer = first_line
   Dim y As Single
   Do While y < g.VisibleClipBounds.Y + g.VisibleClipBounds.Height
    y = first_line_y + 2 + font_height * (i - first_line - 1)
    g.DrawString((i).ToString, .Font, Brushes.DarkBlue, MyPictureBox.Width _
          - g.MeasureString((i).ToString, .Font).Width, y)
    i += 1
   Loop
   'Debug.WriteLine("Finished: " & firstLine + 1 & " " & i - 1)
  End With
 End Sub

This method should be called from the following locations:

1. Upon RichTextBox Resize event. DrawRichTextBoxLineNumbers(MyPictureBox.CreateGraphics)
2. When VScroll event happens on the RichTextBox (MyRichTextBox.VScroll). DrawRichTextBoxLineNumbers(MyPictureBox.CreateGraphics)
3. When Paint Event happens (MyPictureBox.Paint). DrawRichTextBoxLineNumbers(e.Graphics). Note that at this method we send e.Graphics and not MyPictureBox.CreateGraphics as we would like to repaint only the required region whithin the PictureBox control. 

These are the locations from which we need to invoke the line numbering method:

 Private Sub r_Resize(ByVal sender As Object, ByVal e As System.EventArgs) _
     Handles MyRichTextBox.Resize
  MyPictureBox.Invalidate()
 End Sub

 Private Sub r_VScroll(ByVal sender As Object, ByVal e As System.EventArgs) _
     Handles MyRichTextBox.VScroll
  MyPictureBox.Invalidate()
 End Sub

 Private Sub p_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) _
     Handles MyPictureBox.Paint
  DrawRichTextBoxLineNumbers(e.Graphics)
 End Sub

 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) _
     Handles MyBase.Load
  MyRichTextBox.Text = vbCrLf & vbCrLf & vbCrLf
 End Sub

Other general notes

1. The code above assumes that the font name and size of the RichTextBox control is the same for the entire text.
2. The WordWrap property of the RichTextBox control should be set to false.
3. I've placed this code in the Form_Load method to assure that the textbox has at least two lines always. MyRichTextBox.Text = vbCrLf & vbCrLf & vbCrLf
4. I Recommend docking the PictureBox to the left and then calculating the width of the PictureBox based on g.MeasureString("000", MyRichTextBox.Font).Width. The width of the PictureBox should be recalculated and the PictureBox should be redrawn when the font of the RichTextBox changes.
5. The PictureBox control may be replaced with a Panel or any other control that exposes the CreateGraphics() method.
6. The control was designed for RichTextBox controls with WordWrap = False 

 

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Hi Botsbushman 14:09 11 Aug '08   Hi there how things Great code!!! Would ya mind if i were to use it in my college project? I am developing a simple IDE. Of course I will reference your work etc! Thanks a mil Sign In·View Thread·PermaLink Thanks Member 4496730 9:51 6 May '08   Hi there. Thank u Michael. I have been looking for this a long time. Good luck Only God Sign In·View Thread·PermaLink Problem with moving thumb Dipendu Paul 2:18 5 Jul '07   When I am clicking on the carets vscroll event is fired but when I am moving the thumb of the scroll bar vscroll event is not fired? I don't have a clue how to solve this problem!!! Please help!!! Sign In·View Thread·PermaLink Simple code modifications Jason Barrera 12:55 22 Jun '07   In your code.. 'calculate font heigth as the difference in Y coordinate between line 2 and line 1 'note that the RichTextBox text must have at least two lines. So the initial Text property of the RichTextBox should not be an empty string. It could be something like vbcrlf & vbcrlf & vbcrlf Dim font_height As Single = MyRichTextBox.GetPositionFromCharIndex(MyRichTextBox.GetFirstCharIndexFromLine(2)).Y - MyRichTextBox.GetPositionFromCharIndex(MyRichTextBox.GetFirstCharIndexFromLine(1)).Y If font_height = 0 Then Exit Sub Instead of ensuring there are at least a couple lines of text in the control, I use this... If font_height = 0 Then font_height = Me.MyRichTextBox.Font.GetHeight() End If I also noticed that if you resize the controls, sometimes you see it printing half of a "0", so to fix this, where you are printing the variable "i", I use an if statement to check if i > 0. These were just a couple things I noticed and thought I would offer my input. -Jason Sign In·View Thread·PermaLink Text Change in coordinate with font changes... brottmayer 4:10 22 Feb '07   What I mean, is how do you compensate for the font size changing so that the number list matches that of the font size in the myrichtextbox? This is the only dilemma that i have, any help would be great. Thanks. brottmayer Sign In·View Thread·PermaLink 5.00/5 (1 vote) Line numbering in C# - complete [modified] biopsy 6:44 15 Feb '07   using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; namespace Gutter { public partial class frmMain : Form { int total_lines = 0; public frmMain() { InitializeComponent(); } private void DrawRichTextBoxLineNumbers(Graphics g) { Single font_height; if (richTextBox1.Lines.Length < 3) { font_height = richTextBox1.Font.Height; } else { font_height = richTextBox1.GetPositionFromCharIndex(richTextBox1.GetFirstCharIndexFromLine(2)).Y - richTextBox1.GetPositionFromCharIndex(richTextBox1.GetFirstCharIndexFromLine(1)).Y; } Point pos = new Point (0,(int)(g.VisibleClipBounds.Y + font_height / 3)); int first_index, first_line, first_line_y; first_index = richTextBox1.GetCharIndexFromPosition(pos); first_line = richTextBox1.GetLineFromCharIndex(first_index); first_line_y = richTextBox1.GetPositionFromCharIndex(first_index).Y; g.Clear(Control.DefaultBackColor); int i = first_line; int x = 0; Single y = 0; total_lines = richTextBox1.GetLineFromCharIndex(Int32.MaxValue) + 1; while (y < g.VisibleClipBounds.Y + g.VisibleClipBounds.Height) { y = first_line_y - 1 + font_height * (i - first_line - 1); x = panel1.Width - (int)g.MeasureString(i.ToString(), richTextBox1.Font).Width - 5; if (i <= total_lines) { g.DrawString((i).ToString(), richTextBox1.Font, Brushes.DarkBlue, x, (int)y); } i++; } } private void panel1_Paint(object sender, PaintEventArgs e) { DrawRichTextBoxLineNumbers(e.Graphics); } private void richTextBox1_Resize(object sender, EventArgs e) { panel1.Invalidate(); } private void richTextBox1_VScroll(object sender, EventArgs e) { panel1.Invalidate(); } private void richTextBox1_TextChanged(object sender, EventArgs e) { if ((richTextBox1.GetLineFromCharIndex(Int32.MaxValue) + 1) != total_lines) { panel1.Invalidate(); } } } } This doesn't require at least 2 lines in the richTextBox. Just get the font height from the richTextBox font height property. I can image that this is going to be fairly slow because you can actually see the gutter being updated (white flashes). I wonder what would happen if DrawTextBoxLineNumbers() were called in a thread. -- modified at 9:18 Monday 19th February, 2007 Sign In·View Thread·PermaLink 3.33/5 (5 votes) Looks great Alexandru Lungu 11:08 30 Jan '07   I realy like it! Soon I'll have to implement something similar + a code block indicator (something like the c# editor from VS) + some intellisense Sign In·View Thread·PermaLink 5.00/5 (2 votes) Hi Ahmed El-Badry 2:47 25 Jan '07   Plz I need your help i want to send email msg from system windows form (mail format = TXT) mail body = RichTextBox1.text i want select mail body.(font + color + siz) from RichTextBox1 Properties thnx Ahmed El-Badry Sign In·View Thread·PermaLink Vb.net syntax Line Numbering of RichTextBox convertion to c# syntax SirDre 13:37 3 Jan '07   I was trying to convert vb.net syntax to c# syntax but i failed to convert it. Please help me to Correct the errors. private void DrawRichTextBoxLineNumbers(ref Graphics g) { float font_height; font_height = MyRichTextBox.GetPositionFromCharIndex(MyRichTextBox.GetFirstCharIndexFromLine(2)).Y - MyRichTextBox.GetPositionFromCharIndex(MyRichTextBox.GetFirstCharIndexFromLine(1)).Y; if (font_height == 0) { return; } int first_index; int first_line; int first_line_y; first_index = MyRichTextBox.GetCharIndexFromPosition(new Point(0, g.VisibleClipBounds.Y + font_height / 3)); first_line = MyRichTextBox.GetLineFromCharIndex(first_index); first_line_y = MyRichTextBox.GetPositionFromCharIndex(first_index).Y; g.Clear(Control.DefaultBackColor); int i = first_line; float y; while (y < g.VisibleClipBounds.Y + g.VisibleClipBounds.Height) { y = first_line_y + 2 + font_height * (i - first_line - 1); g.DrawString((i).ToString, MyRichTextBox.Font, Brushes.DarkBlue, MyPictureBox.Width - g.MeasureString((i).ToString, MyRichTextBox.Font).Width, y); i += 1; } } private void r_Resize(object sender, System.EventArgs e) { DrawRichTextBoxLineNumbers(MyPictureBox.CreateGraphics); } private void r_VScroll(object sender, System.EventArgs e) { DrawRichTextBoxLineNumbers(MyPictureBox.CreateGraphics); } private void p_Paint(object sender, System.Windows.Forms.PaintEventArgs e) { DrawRichTextBoxLineNumbers(e.Graphics); } private void Form1_Load(object sender, System.EventArgs e) { //MyRichTextBox.Text = vbCrLf + vbCrLf + vbCrLf; } Please help me to fix the problem. SirDre' Sign In·View Thread·PermaLink 2.00/5 (2 votes) Resource leak due to CreateGraphics mav.northwind 23:01 25 Dec '06   Hi! I just stumbled across your article because of a question in the forums and saw that there's a resource leak that you should fix. Instead of creating a new Graphics object every time and not disposing of it you should simply invalidate the PictureBox to let it do it's own painting. Simply replace your calls to DrawRichTextBoxLineNumbers(MyPictureBox.CreateGraphics) with MyPictureBox.Invalidate() and you should be fine. Regards, mav -- Black holes are the places where God divided by 0... Sign In·View Thread·PermaLink 5.00/5 (1 vote) Re: Resource leak due to CreateGraphics Michael Elly 1:27 26 Jan '07   Thanks for the tip. I have modified the code accordingly. Sign In·View Thread·PermaLink Any way to make the code show line numbers only upto contained lines in the RTBox? kil0byte^bandit 5:37 5 Dec '06   Hi, I was trying to modify the code to make it show line numbers ONLY upto the number of lines of text contained in the Rich Text Box - instead of showing all possible line numbers upto the VisibleClipBounds. As I increase text in the RTBox, new line numbers should be displayed. Can you please point me to the right direction? Thanks, k^b PeoPLe aRe cRazY anD tiMeS aRe sTRaNGe, i'M LoCKeD iN tiGhT, i'M OuT oF raNGe, i uSeD t0 caRe BuT - thiNGs haVe chaNGeD. Sign In·View Thread·PermaLink Re: Any way to make the code show line numbers only upto contained lines in the RTBox? Michael Elly 21:19 6 Dec '06   Try this new DrawRichTextBoxLineNumbers method: Private Sub DrawRichTextBoxLineNumbers(ByRef g As Graphics) Dim total_lines As Integer With MyRichTextBox Dim font_height As Single font_height = .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(2)).Y _ - .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(1)).Y If font_height = 0 Then Exit Sub 'Get the first line index and location Dim first_index As Integer Dim first_line As Integer Dim first_line_y As Integer first_index = .GetCharIndexFromPosition(New _ Point(0, g.VisibleClipBounds.Y + font_height / 3)) first_line = .GetLineFromCharIndex(first_index) first_line_y = .GetPositionFromCharIndex(first_index).Y 'get the total number of lines in the richtextbox total_lines = MyRichTextBox.Lines.Length 'Print on the PictureBox the visible line numbers of the RichTextBox g.Clear(Control.DefaultBackColor) Dim i As Integer = first_line Dim y As Single Do While y < g.VisibleClipBounds.Y + g.VisibleClipBounds.Height y = first_line_y + 2 + font_height * (i - first_line - 1) If total_lines <= i Then g.DrawString((i).ToString, .Font, Brushes.DarkBlue, MyPictureBox.Width _ - g.MeasureString((i).ToString, .Font).Width, y) Else Exit Do End If i += 1 Loop End With End Sub Michael Elly Sign In·View Thread·PermaLink Re: Any way to make the code show line numbers only upto contained lines in the RTBox? gabegabe 5:20 4 Jan '07   ..mm that doesn't seem to work until i change your: If total_lines <= i Then to If total_lines >= i Then and delete the else stmt, ..course maybe I should stop coding after 2am.. Sign In·View Thread·PermaLink 5.00/5 (1 vote) Re: Any way to make the code show line numbers only upto contained lines in the RTBox? Michael Elly 1:43 26 Jan '07   Thanks for the correction (I did not check the code snippet I replied to you with, just wrote it off hand... ). Anyway after playing with your use case a bit more I realized that there is no event that takes care of updating the line numbers when a new line is just added. So two things need to happen (1) the total_lines variable need to be a class level variable (2) need to add one more event for MyRichTextBox_TextChanged. The overall code for making it show line numbers only up to where there are actual lines is: Public Class Form1 Dim total_lines As Integer Private Sub DrawRichTextBoxLineNumbers(ByRef g As Graphics) With MyRichTextBox Dim font_height As Single font_height = .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(2)).Y _ - .GetPositionFromCharIndex(.GetFirstCharIndexFromLine(1)).Y If font_height = 0 Then Exit Sub 'Get the first line index and location Dim first_index As Integer Dim first_line As Integer Dim first_line_y As Integer first_index = .GetCharIndexFromPosition(New _ Point(0, g.VisibleClipBounds.Y + font_height / 3)) first_line = .GetLineFromCharIndex(first_index) first_line_y = .GetPositionFromCharIndex(first_index).Y 'get the total number of lines in the richtextbox 'total_lines = MyRichTextBox.Lines.Length total_lines = MyRichTextBox.GetLineFromCharIndex(Int32.MaxValue) + 1 'Print on the PictureBox the visible line numbers of the RichTextBox g.Clear(Control.DefaultBackColor) Dim i As Integer = first_line Dim y As Single Do While y < g.VisibleClipBounds.Y + g.VisibleClipBounds.Height y = first_line_y + 2 + font_height * (i - first_line - 1) If total_lines >= i Then g.DrawString((i).ToString, .Font, Brushes.DarkBlue, MyPictureBox.Width _ - g.MeasureString((i).ToString, .Font).Width, y) Else Exit Do End If i += 1 Loop End With End Sub Private Sub r_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyRichTextBox.Resize MyPictureBox.Invalidate() End Sub Private Sub r_VScroll(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyRichTextBox.VScroll MyPictureBox.Invalidate() End Sub Private Sub p_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyPictureBox.Paint DrawRichTextBoxLineNumbers(e.Graphics) End Sub Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load MyRichTextBox.Text = vbCrLf & vbCrLf & vbCrLf End Sub Private Sub MyRichTextBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyRichTextBox.TextChanged If MyRichTextBox.GetLineFromCharIndex(Int32.MaxValue) + 1 <> total_lines Then MyPictureBox.Invalidate() End Sub End Class One more comment: The control was designed for RichTextBox with WordWrap=False. Sign In·View Thread·PermaLink wordwrap linecount fix gabegabe 22:29 17 Jan '07   with word wrap on the MyRichTextBox.Lines.Length isn't right, use total_lines = MyRichTextBox.GetLineFromCharIndex(Int32.MaxValue) + 1 Sign In·View Thread·PermaLink [Message Deleted] Arkady Lesniara 5:24 26 Jun '06   Sign In·View Thread·PermaLink Re: Compile Problem GuardianStorm 7:27 26 Jun '06   are you using .NET 2.0? and what exactly is the problem? http://www.stormbase.net Sign In·View Thread·PermaLink Re: Compile Problem micmelly 7:43 27 Jun '06   I just sent a new package. The sample application now works out of the box. Sign In·View Thread·PermaLink Re: Compile Problem Arkady Lesniara 7:54 27 Jun '06   Works great, the line font changed and increased with the text box. Very nice. Thx. Sign In·View Thread·PermaLink 2.00/5 (2 votes)

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