Limit the max number of chars per line in a textbox

Question

Say I have the following:

Answer 1

I have looked at several solutions today. They either don't work at all, or if they work, they don't work the way I think they should. Oddities with cursor position, or wrapping incorrectly. Here is my "solution", and I hope it helps someone in the future. It wraps, doesn't unwrap, and keeps any existing new lines. I set this example to 60 characters wide, and a bool isBusyUpdating outside of this example to keep it from firing again when the update is in progress.

        txtNotes.HorizontalContentAlignment = HorizontalAlignment.Left;
        txtNotes.VerticalContentAlignment = VerticalAlignment.Top;
        txtNotes.TextWrapping = TextWrapping.NoWrap;
        txtNotes.AcceptsReturn = true;
        txtNotes.TextChanged += delegate (object o, TextChangedEventArgs args)
        {
            //args.Handled = true;
            TextBox thisText = (TextBox)args.Source;
             if (!isBusyUpdating)
            {
                isBusyUpdating = true;
                string updatedText = "";
                bool blnUpdate = false;
                int curPos = thisText.CaretIndex;

                foreach (string thisLine in thisText.Text.Split('\n'))
                {

                    if (thisLine.Length > 60)
                    {
                        blnUpdate = true;
                        updatedText = updatedText + 
                            thisLine.Substring(0, 60)
                            .Replace("\n", "") +
                                      "\n" + thisLine.Substring(60);
                        curPos++;
                    }
                    else
                    {
                        updatedText = updatedText + thisLine + "\n";
                    }
                }

                if (blnUpdate)
                {
                    thisText.Text = updatedText;
                    thisText.CaretIndex = curPos-1;
                }
                isBusyUpdating = false;

            }

        };