How to fix pointer on screen to desired position? - winforms

Question

I am working on mail merge using Winform as a tool. I've provided 2 templates, one for business letters and another for memos. For letters, the user usually types the body of the letter while other information is picked from a data file that is created by user by clicking on "Select Recipient" option.
I want to restrict my user to only type the body, and the pointer must be positioned following the second line of salutation. The pointer can't move backward from that position but, of course, can move forward. How do I do this?
I am sorry for being unclear, if I am.

Answer 1

If your text is in a TextBox or a RichTextBox you can select the control and place the cursor with
// Set the cursor into the text box
bodyTextBox.Focus();
// Place the cursor at the desired position in the text
bodyTextBox.Select(start, 0);
You will have to figure out where the third line starts
const int indent = 30; // Desired indentation
// Place focus in this control
bodyTextBox.Focus();
// The following work only if we have at least 3 lines of text
if (bodyTextBox.Lines.Length >= 3) {
int start = bodyTextBox.Lines[0].Length + // Length of first line
bodyTextBox.Lines[1].Length + // Length of second line
4 + // 2 x 2 characters for two CR-LFs
Math.Min(indent, bodyTextBox.Lines[2].Length);
bodyTextBox.Select(start, 0);
}
I assume that the text looks like this
First line of text.<CR><LF>
Second line of text.<CR><LF>
<30 spaces for indent>
^ desired position
In order to set the cursor at the right place, we need to count the total number of characters from the beginning of the text. Since you want to position the cursor on the third line, this is the length of two first lines plus the two CR-LFs (the line break characters) at their end plus the 30 characters at the beginning of the third line. If the third line is less than 30 characters long, we cannot place the cursor there, therefore we place it at far as possible to the right, i.e. on the last character of this line with Math.Min(indent, bodyTextBox.Lines[2].Length);
Finally we place the cursor there with Select. Since we do not want to select text, we define the length of the selection as zero.