CODEWITHSUNDEEP
c#
Q8Y
Q8Y

Reputation: 4001

How to select text from the RichTextBox and then color it?

I want to create a simple editor like Notepad++ with simple functionality... I need to color a specific word in the rich text box area. How can I do that?

For example: when the user write these word, I want to color them to the blue color. These words are: for, while, if, try, etc.

How can I make the richtextbox to select a specific word and then color them? And, if I want to make a comment and color everything after the //, how is that done in the richtextbox?

How do I number the line in the text box, so I can now the line number when I'm coding in my editor?

Upvotes: 8

Views: 32943

Answers (6)

Seyfemichael Teklemariam
Seyfemichael Teklemariam

Reputation: 3

Vb.net implementation

Imports System.Text.RegularExpressions

Private Sub formatString()
  Dim rg =New Regex("\b(for|while|if|try)\b")
  Dim m As Match

 For Each m In rg.Matches(RichTextBox1.Text)
   RichTextBox1.Select(m.Index,m.Length)
   RichTextBox1.SelectionColor=Color.Green 
 Next

End Sub

Upvotes: 0

Herman Van Der Blom
Herman Van Der Blom

Reputation: 802

I had some problems with that and here is my solution, beats me why it has to be done like this, but it works:

            // position on end of control...
            richTextBox.UpdateLayout();
            richTextBox.ScrollToEnd();
            richTextBox.UpdateLayout();

            // ...then select text and it will be position on top of control.
            richTextBox.Focus();
            richTextBox.Selection.Select(foundRange.Start, foundRange.End);
            richTextBox.BringIntoView();

Upvotes: 0

Alex Essilfie
Alex Essilfie

Reputation: 12613

Here's some code you can build on in order to achieve the functionality you want.

private void ColourRrbText(RichTextBox rtb)
{
    Regex regExp = new Regex("\b(For|Next|If|Then)\b");

    foreach (Match match in regExp.Matches(rtb.Text))
    {
        rtb.Select(match.Index, match.Length);
        rtb.SelectionColor = Color.Blue;
    }
}

The CodeProject article Enabling syntax highlighting in a RichTextBox shows how to use RegEx in a RichTextBox to perform syntax highlighting. Specifically, look at the SyntaxRichtTextBox.cs for the implementation.

Upvotes: 24

Abdul Rehman
Abdul Rehman

Reputation: 2334

here is a good link on c-sharpcorner.com website on basic richtextbox syntax highlighting. I assume that you and any one visiting this page for similar problem want to do it for learning purpose. But if any one wants to do it for some making some comercial level IDE then it must use scintilla or some similar. An other approach for this is to directly change the RTF of the richtextbox. Look in codeproject.com there are lot of articles similar to this problem.

Upvotes: 0

Jude Cooray
Jude Cooray

Reputation: 19862

Did you know that Notepad++ uses Scintilla?

You actually do not have to reinvent the wheel by going through all the trouble as there is a .NET port of Scintilla named ScintillaNET which you can freely embed in your application as the source code editor :)

But to answer your question, there are few parts that you need to understand

  1. Finding what to color
  2. When to color

  3. How to color

  4. For the first part, there may be different approaches, but I think using regular expressions would be a good choice. I am sorry, but I don't know regular expressions much so I cannot help you in that case.

  5. When to color is very crucial and if you do it wrong, your application will suffer a heavy performance penalty. I suggest you refer to XPath Visualizer which was done by our own Stack Overflow member, Cheeso. Take a look at the source on how the coloring of the syntax was done. But if you ScintillaNET, everything would be taken care of. Anyway, I really can't seem to find this documentation where he clearly showed how the coloring of the text was done. I would most definitely post it here if I find it.

  6. The third question I think is covered by VinayC. But basically you use SelectionColor along with SelectionStart.

Upvotes: 2

VinayC
VinayC

Reputation: 49195

In general, you have to work on the selection in RichTextBox. You can manipulate the current selection using the Find method or using SelectionStart and SelectionLength properties. Then you can change properties of selected text using SelectionXXX properties. For example, SelectionColor would set the color of current selection, etc. So you have to parse text in richtextbox and then select part of texts and change their properties as per your requirements.

Writing a good text editor using RichTextBox can be quite cumbersome. You should use some library such as Scintilla for that. Have a look at ScintillaNet, a .NET wrapper over Scintilla.

Upvotes: 4

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