part of textbox readonly in windows Application Using C#

It is a little difficult and personally i do not not recommended what I am about to do now. but if you still have to do it them do it like this:

1. handle textBox2_TextChanged event
2. have the Text property of textbox set to "contentSetName."
3. then have this code:

private void textBox2_TextChanged(object sender, EventArgs e)
       {
           string newtext = textBox2.Text.Replace("contentSetName.", "");

           textBox2.Text = "contentSetName." + newtext;
       }

Note: The better way could be to use a maskedtextbox instead. think about that too.

The better solution will be

define a start and end position for your textbox. then after in keypress event if the key is pressed on the defined area then cancel the keyprees...