Adding guidelines to a TextBox/RichTextBox

Question

Is there any way to show gridlines on a multiline textbox or a richtextbox? Perhaps by overriding the OnPaint event?

I am using the textbox to insert address information, for each line it would be something like:

Street
City
Country
etc.

I am using WinForms with C#.

Answer 1

You can do it using one of these methods:

• Customize Paint of TextBox
• Using RTF Tricks

and here is a screenshot of these 2 ways:

I recommend using first method if you really want this feature.

1- Customizing Paint of TextBox

---

Customizing textbox paint in not straightforward. You can customize paint of TextBox in different ways. here is 2 way of customize painting of TextBox.

1-1 Customizing Paint of TextBox using NativeWindow

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In this way should subclass a TextBox using NativeWindow and handle WM_PAINT in window procedure. Here is a complete code listing that implements what you need.

To use code it is enough to pass your textbox to an instance of CustomPaintTextBox:

var t = new CustomControls.CustomPaintTextBox(this.textBox1);

And here is the code of CustomPaintTextBox

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
namespace CustomControls
{
    public class CustomPaintTextBox : NativeWindow
    {
        private TextBox parentTextBox;
        private const int WM_PAINT = 15;
        protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_PAINT: 
                    // invalidate textbox to make it refresh
                    parentTextBox.Invalidate();
                    // call default paint
                    base.WndProc(ref m);
                    // draw custom paint
                    this.CustomPaint();
                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }
        public CustomPaintTextBox(TextBox textBox)
        {
            this.parentTextBox = textBox;
            textBox.TextChanged += textBox_TextChanged;
            // subscribe for messages
            this.AssignHandle(textBox.Handle);
        }
        void textBox_TextChanged(object sender, EventArgs e)
        {
            CustomPaint();
        }
        private void CustomPaint()
        {
            var g= this.parentTextBox.CreateGraphics();
            float y = 0;
            var lineHeight = g.MeasureString("X", this.parentTextBox.Font).Height;
            while (y < this.parentTextBox.Height)
            {
                y += lineHeight;
                g.DrawLine(Pens.Red, 0f, y, (float)this.parentTextBox.Width, y);
            }
        }
    }
}

The up side of this solution is its is quiet simple and doesn't need new inherited textbox.

1-2- Creating Transparent TextBox

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This way you should first Make a transparent text box and then set the background of it to your gridlines that you want. Since this way is also a way of creating custom paint textbox, you can customize the painting of that textbox too and bend it to your will.

Here is link to 2 greate articles that cover Transparent TextBox and Transparent RichTextBox:

• Alpha Blended (Transparent Capable) TextBox and RichTextBox
• AlphaBlendTextBox - A transparent/translucent textbox for .NET

2- Using RTF tricks

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There is some rtf tricks than you ca use to show grid lines in RichTextBox. One of best tricks is using tables in RTF. In below code We used 3 rows that contains a cell of width 2000 twips:

this.richTextBox1.SelectAll();
this.richTextBox1.SelectedRtf =
@"{\rtf1\ansi\deff0
{\trowd
\cellx2000
\intbl Street\cell
\row}
{\trowd
\cellx2000
\intbl City\cell
\row}
{\trowd
\cellx2000
\intbl Country\cell
\row}
}";

Important: When pasting above code in code editor, be careful to put no indents before richtext characters. If Visual studio inserted indent before them, you remove all indents.

Answer 2

Start with this code:

class GridLineTextBox : TextBox
{
    public GridLineTextBox()
    {
        SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.ResizeRedraw, true);
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        var y = 0f;
        var lineHeight = e.Graphics.MeasureString("W", Font).Height;
        while (y < e.ClipRectangle.Height)
        {
            y += lineHeight;
            e.Graphics.DrawLine(System.Drawing.Pens.Aqua, new PointF(0, y), new PointF(e.ClipRectangle.Width, y));
        }
    }
}

Answer 3

Maybe an RTF template file:

{\rtf1\ansi\ansicpg1252\deff0{\fonttbl{\f0\fnil\fcharset0 Calibri;}}
{\trowd \trgaph180
\cellx3440\pard\intbl [0]\cell
\row
\trowd \trgaph180
\cellx3440\pard\intbl [1]\cell
\row
\trowd \trgaph180
\cellx3440\pard\intbl [2]\cell
\row
\para}

---

Dim fileContents As String
fileContents = My.Computer.FileSystem.ReadAllText("C:\temp\template.rtf")
Dim sRTF As String = fileContents.Replace("[0]", "line 1").Replace("[1]", "line 2").Replace("[2]", "line 3")
RichTextBox1.Rtf = sRTF