Track, Record, Set RichTextBox Caret Position

This project demonstrates how to track the current location of a richtextbox caret, record it's current location, with the option to return it to it's previously recorded location. It's not perfect, meaning if you record the caret position at say line 12, then you add characters to the length of line 9, your record position will drop the same amount of characters, probably sending it back to line 11 or lower.

What this idea could be used for is to write to 2 textboxes at the same time at the same caret location.

Attachment 168025

What's needed for below code:
* Panel docked top
* 2 Buttons inside it for recording and setting caret
* 3 Labels below buttons
* a GroupBox "Recorded Position" inside panel, docked right
* 2 Labels named RecLineLabel and RecColumnLabel inside GroupBox
* RichTextBox below panel, docked fill

Code:

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Option Strict On

'This project tracks the current location of a RichTextBox caret, with the
'option to record it's location and return it to it's recorded location.

Public Class Form1

  'for recording and setting caret position
    Public start As Integer
    Public length As Integer


    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
      'display caret in RichTextBox
        RichTextBox1.SelectionStart = start
        RichTextBox1.[Select]()

        'below gets caret's current line and column position
        Dim line As Integer = RichTextBox1.GetLineFromCharIndex(RichTextBox1.SelectionStart)
        Dim column As Integer = RichTextBox1.SelectionStart - RichTextBox1.GetFirstCharIndexFromLine(line)
        Label2.Text = "Line " + CStr(CDbl(line.ToString) + 1)
        Label3.Text = "Column " + CStr(CDbl(column.ToString) + 1)
        line = Nothing : column = Nothing
    End Sub


    Private Sub RichTextBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles RichTextBox1.MouseDown
        'below gets caret's current line and column position
        Dim line As Integer = RichTextBox1.GetLineFromCharIndex(RichTextBox1.SelectionStart)
        Dim column As Integer = RichTextBox1.SelectionStart - RichTextBox1.GetFirstCharIndexFromLine(line)
        Label2.Text = "Line " + CStr(CDbl(line.ToString) + 1)
        Label3.Text = "Column " + CStr(CDbl(column.ToString) + 1)
        line = Nothing : column = Nothing
    End Sub


    Private Sub RichTextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RichTextBox1.TextChanged
        'below gets caret's current line and column position
        Dim line As Integer = RichTextBox1.GetLineFromCharIndex(RichTextBox1.SelectionStart)
        Dim column As Integer = RichTextBox1.SelectionStart - RichTextBox1.GetFirstCharIndexFromLine(line)
        Label2.Text = "Line " + CStr(CDbl(line.ToString) + 1)
        Label3.Text = "Column " + CStr(CDbl(column.ToString) + 1)
        line = Nothing : column = Nothing
    End Sub


    'record caret position
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'for recording caret
        start = RichTextBox1.SelectionStart
        length = RichTextBox1.SelectionLength

      'resetting caret so it stays visible after position is recorded
        RichTextBox1.SelectionStart = start
        RichTextBox1.SelectionLength = length
        RichTextBox1.[Select]()

        'to display the recorded caret position
        Dim line As Integer = RichTextBox1.GetLineFromCharIndex(RichTextBox1.SelectionStart)
        Dim column As Integer = RichTextBox1.SelectionStart - RichTextBox1.GetFirstCharIndexFromLine(line)
        RecLineLabel.Text = "Line " + CStr(CDbl(line.ToString) + 1)
        RecColumnLabel.Text = "Column " + CStr(CDbl(column.ToString) + 1)
        line = Nothing : column = Nothing
    End Sub


    'no matter where the caret is in the RichTextBox, pressing this button will
    'return it to it's recorded position
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
      'set caret to previously recorded position
        RichTextBox1.SelectionStart = start
        RichTextBox1.SelectionLength = length
        RichTextBox1.[Select]()

        'below gets caret's current line and column position
        Dim line As Integer = RichTextBox1.GetLineFromCharIndex(RichTextBox1.SelectionStart)
        Dim column As Integer = RichTextBox1.SelectionStart - RichTextBox1.GetFirstCharIndexFromLine(line)
        Label2.Text = "Line " + CStr(CDbl(line.ToString) + 1)      'I know I could've simply wrote Label2.Text = RecLineLabel.Text
        Label3.Text = "Column " + CStr(CDbl(column.ToString) + 1)  'it's just to show the tracked position matches recorded
        line = Nothing : column = Nothing
    End Sub


End Class

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Created with Visual Basic 2010 Express
.Net Framework 4.0
Windows 7