select column in a file

If you want to select a particular column in a text file, then it would depend on what combination of keystrokes is required to highlight that column in the text editor you're using.

You'd then need to force input focus onto the text editor which can be done by calling the API functions FindWindow and SetForegroundWindow.

The appropriate keystrokes can then be sent to the text editor using the managed SendKeys.Send or SendKeys.SendWait methods.

I'll warn you now that doing anything like this programatically can be a bit flakey due to timing issues but it's usually possible to figure something out.