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Asked: 2026-05-17T03:10:35+00:00

This is going to be a long post. I would like to have suggestions

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This is going to be a long post. I would like to have suggestions if any on the procedure I am following. I want the best method to print line numbers next to each CRLF-terminated-line in a richtextbox. I am using C# with .NET. I have tried using ListView but it is inefficient when number of lines grow. I have been successful in using Graphics in custom control to print the line numbers and so far I am happy with the performance.

But as the number of lines grow to 50K to 100K the scrolling is affected badly. I have overridden WndProc method and handling all the messages to call the line-number printing only when required. (Overriding OnContentsResized and OnVScroll make redundant calls to the printing method).

Now the line number printing is fine when number of lines is small say upto 10K (with which I am fine as it is rare need to edit a file with 10000 lines) but I want to remove the limitation.

Few Observations

  • Number of lines displayed in the richtexbox is constant +-1. So, the performance difference should be due to large text and not because I am using Graphics painting.
  • Painting line numbers for large text is slower when compared to small files

Now the Pseudo Code

FIRST_LINE_NUMBER = _textBox.GetFirstVisibleLineNumber();
LAST_LINE_NUMBER = _textBox.GetLastVisibleLineNUmber();
for(loop_from_first_to_last_line_number)
{
    Y = _textBox.GetYPositionOfLineNumber(current_line_number);
    graphics_paint_line_number(current_line_number, Y);
}

I am using GetCharIndexFromPosition and loop through the RichTextBox.Lines to find the line number in both the functions which get the line numbers. To get Y position I am using GetPositionFromCharIndex to get the Point struct.

All the above RichTextBox methods seem to be of O(n), which eats up the performance. (Correct me if I am wrong.)

I have decided to use a binary-tree to store the line numbers to improve the search perfomance when searching for line number by char index. I have an idea of getting a data-structure which takes O(n) construction time, O(nlgn) worst-case-update, and O(lgn) search.

Is this approach worth the effort?
Is there any other approach to solve the problem? If required I am ready to write the control from scratch, I just want it to be light-weight and fast.

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1 Answer

  1. Editorial Team

    Before deciding on the best way forward, we need to make sure we understand the bottleneck.

    First of all, it is important to know how RichTextbox (which I assume you are using as you mentioned it) handles the large files. So I would recommend to remove all line printing stuff and see how it performs with large text. If it is poor, there is your problem.

    Second step would be to put some profiling statements or just use a profiler (one comes with the VS 2010) to find the bottleneck. It might turn out to be the method for finding the line number, or something else.

    At this point, I would only suggest more investigation. If you have finished the investigation and have more info, update your question and I will get back to you accordingly.

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