Syntax Highlight in C#, How to implement syntax highlighting in a WinForms application. Options

[PixelCard]

In this tutorial you will see how to implement the syntax highlighting feature in a C# WinForms application. For this purpose I will use the RegularExpressions class, member of the System.Text namespace.

Special Tutorial Requirements:

• C# IDE (Visual Studio 2008 used in this tutorial)
• .NET Framework 1.0

So, here we go.

1. Create a C# Windows Forms application:



2. Add a RichTextBox control to the form:



3. Add a Timer control to the form:



4. Change the following timer properties:

• Enabled = True
• Interval = 1000

5. Add the System.Text.RegularExpressions namespace to the project:

csharp

using System.Text.RegularExpressions;

6. Create a new regex right after "public partial class Form1 : Form {". I will name it keyWords:[b]

csharp

public Regex keyWords = new Regex& quot;abstract|as|base|bool|break|byte|case|catch|char|checked|class|const|contin
 ue|decimal|default|delegate|do|double|else|enum|event|explicit|extern|false|fina
lly|fixed|float|for|" +
& quot;foreach|goto|if|implicit|in|int|interface|internal|is|lock|long|namespace|n
 ew|null|object|operator|out|override|params|private|protected|public|readonly|re
f|return|sbyte|sealed|short|sizeof|stackalloc|static|" + & quot;string|struct|switch|this|throw|true|try|typeof|uint|ulong|unchecked|unsafe
|ushort|using|virtual|volatile|void|while|");

My regex contains all C# reserved words from this MSDN page:
C# Keywords

[b]7. This code goes for the timer (timer1_Tick):

csharp

private void timer1_Tick(object sender, EventArgs e)
        {
            //Highlight every found word from keyWords.
            
            //Get the last cursor position in the richTextBox1.

            int selPos = richTextBox1.SelectionStart;

            //For each match from the regex, highlight the word.
            foreach (Match keyWordMatch in keyWords.Matches(richTextBox1.Text))
            {

                richTextBox1.Select(keyWordMatch.Index, keyWordMatch.Length);
                richTextBox1.SelectionColor = Color.Blue;
                richTextBox1.SelectionStart = selPos;
                richTextBox1.SelectionColor = Color.Black;
            }
}

Of course you can add more regex variables for different words and different colors for highlighting.

Every 1 second the text will be parsed for matches and every found match will be highlighted. This code can be modified. Instead of using the timer's tick event the richTextBox's TextChanged event can be used. The code will look like this:

csharp

private void richTextBox1_TextChanged(object sender, EventArgs e)
        {
            //Highlight every found word from keyWords.
            
            //Get the last cursor position in the richTextBox1.

            int selPos = richTextBox1.SelectionStart;

            //For each match from the regex, highlight the word.
            foreach (Match keyWordMatch in keyWords.Matches(richTextBox1.Text))
            {

                richTextBox1.Select(keyWordMatch.Index, keyWordMatch.Length);
                richTextBox1.SelectionColor = Color.Blue;
                richTextBox1.SelectionStart = selPos;
                richTextBox1.SelectionColor = Color.Black;
            }
}

[gabehabe]

Nice tutorial! I just wish I could've found it before I wrote 500 lines of a class to do it
Then again, my class deals with comments and block comments, too

Two things though:
When it highlights the text, it's going to flash, isn't it?

Why not block that out with LockWindowUpdate() ?

csharp

[DllImport("user32.dll")] // import lockwindow to remove flashing
public static extern bool LockWindowUpdate (IntPtr hWndLock);

Then, in your TextChanged event, you could do the following:

csharp

private void richTextBox1_TextChanged(object sender, EventArgs e)
{
	try {
		LockWindowUpdate(richTextBox1.Handle);
		//Highlight every found word from keyWords.
	            
		//Get the last cursor position in the richTextBox1.
		int selPos = richTextBox1.SelectionStart;
	
		//For each match from the regex, highlight the word.
		foreach (Match keyWordMatch in keyWords.Matches(richTextBox1.Text))
		{
			richTextBox1.Select(keyWordMatch.Index, keyWordMatch.Length);
			richTextBox1.SelectionColor = Color.Blue;
			richTextBox1.SelectionStart = selPos;
			richTextBox1.SelectionColor = Color.Black;
		}
	} finally {LockWindowUpdate(IntPtr.Zero);}
}

Also, with longer code, it could start to take a while. That could be fixed by working word for word. (Just read back to find the most recent space)

[TonicX57]

Nice. Thanks a lot for this tutorial. This really helps. I was trying to make an editor for my programming language, but I couldn't figure out how. Thanks, mate.

[jammmie999]

Nice tutorial! I just wish I could've found it before I wrote 500 lines of a class to do it
Then again, my class deals with comments and block comments, too

Two things though:
When it highlights the text, it's going to flash, isn't it?

Why not block that out with LockWindowUpdate() ?

csharp

[DllImport("user32.dll")] // import lockwindow to remove flashing
public static extern bool LockWindowUpdate (IntPtr hWndLock);

Then, in your TextChanged event, you could do the following:

csharp

private void richTextBox1_TextChanged(object sender, EventArgs e)
{
	try {
		LockWindowUpdate(richTextBox1.Handle);
		//Highlight every found word from keyWords.
	            
		//Get the last cursor position in the richTextBox1.
		int selPos = richTextBox1.SelectionStart;
	
		//For each match from the regex, highlight the word.
		foreach (Match keyWordMatch in keyWords.Matches(richTextBox1.Text))
		{
			richTextBox1.Select(keyWordMatch.Index, keyWordMatch.Length);
			richTextBox1.SelectionColor = Color.Blue;
			richTextBox1.SelectionStart = selPos;
			richTextBox1.SelectionColor = Color.Black;
		}
	} finally {LockWindowUpdate(IntPtr.Zero);}
}

Also, with longer code, it could start to take a while. That could be fixed by working word for word. (Just read back to find the most recent space)

Hi when I try and add

CODE

        [DllImport("user32.dll")] // import lockwindow to remove flashing
        public static extern bool LockWindowUpdate(IntPtr hWndLock);

I get an error message:
Error 1 Expected class, delegate, enum, interface, or struct
Error 2 The modifier 'extern' is not valid for this item

What is wrong

Thanks

[Ändrew]

Hi when I try and add

CODE

        [DllImport("user32.dll")] // import lockwindow to remove flashing
        public static extern bool LockWindowUpdate(IntPtr hWndLock);

I get an error message:
Error 1 Expected class, delegate, enum, interface, or struct
Error 2 The modifier 'extern' is not valid for this item

What is wrong

Thanks

CODE

using System.Runtime.InteropServices;

Make sure you have that...

[thaproxinator]

hi, i am currently using this code in vb.net and am wondering if single characters can be highlighted e.g. ">"

i have tried to do this but it just highlights the whole text in the RichTextBox

any help would be appreciated

tia

EDIT: nevermind, my code was wrong. i managed to fix it

This post has been edited by thaproxinator: 25 Jun, 2009 - 04:04 AM

[tuyen]

Dear !
I am trying implement "highlight" method to above Web Browser. I desire to add a button that when it is clicked, selected text on Browser will will be highlighted. But i don't know how to do. Could some one help me !

Thank you very much !

[CheckersW]

Dear !
I am trying implement "highlight" method to above Web Browser. I desire to add a button that when it is clicked, selected text on Browser will will be highlighted. But i don't know how to do. Could some one help me !

Thank you very much !

Instead of asking for help here, you should start a new topic in the forums and just include a link to the page there. That way, more people will see your question and help you, and others will be able to learn from the answer to your question more easily.

[binary_refinary]

Hey,

many thanks for the quick tutorial !

hands down- the best tutor i've found on the net for c# text highlighting