How to get the current line in a RichTextBox control?

Say I clicked somewhere inside 开发者_如何学编程a RichTextBox control. How can I get the current line the caret is currently on?

Btw this is to retrieve the whole text string of that line.

This worked for me:

this.WordWrap = false;
int cursorPosition = this.SelectionStart;
int lineIndex = this.GetLineFromCharIndex(cursorPosition);
string lineText = this.Lines[lineIndex];
this.WordWrap = true;

That's what RichTextBox.GetLineFromCharIndex() does. Pass the SelectionStart property value.

One way is to send it the EM_LINEFROMCHAR Message. I'm sure there are other ways.

My answer is even more awesome than Vincent's because after getting the right line number I noticed it was flickering, horribly. So I added an in memory rich text box to do the work there.

private int GetCharacterIndexOfSelection()
{
    var wordWrappedIndex = this.SelectionStart;

    RichTextBox scratch = new RichTextBox();
    scratch.Lines = this.Lines;
    scratch.SelectionStart = wordWrappedIndex;
    scratch.SelectionLength = 1;
    scratch.WordWrap = false;
    return scratch.SelectionStart;
}

private int GetLineNumberOfSelection()
{
    var selectionStartIndex = GetCharacterIndexOfSelection();

    RichTextBox scratch = new RichTextBox();
    scratch.Lines = this.Lines;
    scratch.SelectionStart = selectionStartIndex;
    scratch.SelectionLength = 1;
    scratch.WordWrap = false;
    return scratch.GetLineFromCharIndex(selectionStartIndex);
}

This works by counting from the beginning of the document.

                var startlinenumber = FindLineNumber(RichText, RichText.Selection.Start);
                var endlinenumber = FindLineNumber(RichText, RichText.Selection.End);

Here is the actual function.

int FindLineNumber(RichTextBox rtb, TextPointer p)
{
    var findStart = p?.GetLineStartPosition(0);
    if (findStart == null) return 0;
    var startLinePosition = rtb.Document.ContentStart.GetLineStartPosition(0);
    if (startLinePosition == null) return 0;

    var foundLineNumber = 0;
    while (true)
    {
        if (startLinePosition.CompareTo(findStart) >= 0)
        {
            break;
        }

        startLinePosition = startLinePosition.GetLineStartPosition(1, out var result);
        if (result == 0)
        {
            break;
        }

        foundLineNumber++;
    }

    return foundLineNumber;
}

If you want to get current Line Number from the editor Control where you are debugging now then

int lineNumber = (new StackTrace()).GetFrame(1).GetFileLineNumber();

I think it is helpful for your problem.