Delete a specific line in a .NET RichTextBox

Question

How can I delete a specific line of text in a RichTextBox ?

Solution 1

Another solution:

private void DeleteLine(int a_line)
{
    int start_index = richTextBox.GetFirstCharIndexFromLine(a_line);
    int count = richTextBox.Lines[a_line].Length;

    // Eat new line chars
    if (a_line < richTextBox.Lines.Length - 1)
    {
        count += richTextBox.GetFirstCharIndexFromLine(a_line + 1) -
            ((start_index + count - 1) + 1);
    }

    richTextBox.Text = richTextBox.Text.Remove(start_index, count);
}

Solution 2

This also could do the trick (if you can handle things such as ++ in forms code). Keeps the text format. Just remember "ReadOnly" attribute work for both you and user.

richTextBox.SelectionStart = richTextBox.GetFirstCharIndexFromLine(your_line);
richTextBox.SelectionLength = this.richTextBox.Lines[your_line].Length+1;
this.richTextBox.SelectedText = String.Empty;

Solution 3

Try this:

Dim lst As New ListBox  
        Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click  
            Me.Controls.Add(lst)  
            For Each cosa As String In Me.RichTextBox1.Lines  
                lst.Items.Add(cosa)  
            Next  
            lst.Items.RemoveAt(2) 'the integer value must be the line that you want to remove -1  
            Me.RichTextBox1.Text = String.Empty  
            For i As Integer = 0 To lst.Items.Count - 1  
                If Me.RichTextBox1.Text = String.Empty Then  
                    Me.RichTextBox1.Text = lst.Items.Item(i)  
                Else  
                    MeMe.RichTextBox1.Text = Me.RichTextBox1.Text & Environment.NewLine & lst.Items.Item(i).ToString  
                End If  
            Next  
        End Sub

http://social.msdn.microsoft.com/Forums/en-US/vbgeneral/thread/63647481-743d-4e55-9043-e0db5106a03a/

Solution 4

Based on tomanu's solution but without overhead

int start_index = LogBox.GetFirstCharIndexFromLine(linescount);
int count = LogBox.GetFirstCharIndexFromLine(linescount + 1) - start_index;
LogBox.Text = LogBox.Text.Remove(start_index, count);

note that my linescount here is linescount - 2.

Solution 5

Find the text to delete in a text range, found here Set the text to empty, and now it is gone form the document.

View more solutions

Comments

[David Basarab]

This would get slow as the number of lines increased.

[TLiebe]

You're right and I should have put a warning in there but for a reasonable number of lines (less than 100?) it should be fine.

[Cary Bondoc]

Link only answer is not good. :D Edit it and I'll up vote you Sir.

[Dave Cousineau]

does this work for the last line in the box? I like tomanu's int count = richTextBox.Lines[a_line].Length; line better.

[Dave Cousineau]

what does the "eat new line chars" block do? doesn't the -1 +1 cancel out? it would seem to evaluate to count += 0 actually...

[Dave Cousineau]

ok I get it, the length doesn't otherwise include the end of line characters, missed that.

[Dave Cousineau]

running it through my tests, no it doesn't, though it might be related to what you say in the last line, not sure what that means.

[Wesley Long]

I tried this once. It bit me by losing my RTF formatting.

[Tombala]

This removes all formatting from the existing text. If you don't want to remove formatting, you have to go with the route of "Create a selection, then clear the selection". See other answers.

[Tombala]

This is the only approach that does not remove formatting from existing text. Setting the Text property clears all existing formatting. Also to note, if your textbox is readonly, set Readonly to false just before modifying SelectedText, then restore Readonly to true after it.

[David Buck]

When answering an old question, your answer would be much more useful to other StackOverflow users if you included some context to explain how your answer helps. See: How do I write a good answer.