Get/Set First Visible Line of RichTextBox

.net, c#, richtextbox, scroll, winforms

Solution

Here may be what you need:

//get the first visible char index
int firstVisibleChar = richTextBox1.GetCharIndexFromPosition(new Point(0,0));
//get the line index from the char index
int lineIndex = richTextBox1.GetLineFromCharIndex(firstVisibleChar);
//just get the string of the line
string firstVisibleLine = richTextBox1.Lines[lineIndex];

For your comment saying that you want some line accordingly to the `Width` of the `RichTextBox`, you can do something like this:

int firstVisibleChar = richTextBox1.GetCharIndexFromPosition(new Point(0,0));
int lastChar = richTextBox1.GetCharIndexFromPosition(new Point(richTextBox1.ClientSize.Width - 1, 1));
string firstVisibleLine = richTextBox1.Text.Substring(firstVisibleChar, lastChar - firstVisibleChar);

Problem

I have a `RichTextBox` with thousands of lines of text in it. I can easily `SET` the first visible line by using `ScrollToCaret()` by doing... ``` this.SelectionStart = this.Find(this.Lines[lineIndex], RichTextBoxFinds.NoHighlight); this.ScrollToCaret(); ``` But I would like to be able to `GET` the first visible line too. Any suggestions?

Original source