Imitating Console.ReadLine() with a RTB & TXT

[noahssite]

I have two controls on a windows form.

rtbOutput = RichTextBox
txtInput = TextBox

When the KeyDown event is triggered, if e.Keycode == Keys.Enter then a combination of a Switch block and if statements are used to process what the user entered in the textbox (txtInput). If for example it equals "exit" then the application will exit: Application.Exit();

If it were another command for example 'time', then "The time is ...." would be appended on a new line of rtbOutput. However how would I create my own version of Console.ReadLine()? For example when the user types 'exit', instead of just exiting the application, a new line is added to rtbOutput: "Are you sure you would like to exit? (Y/N)". Then the user has the option of typing y/n to exit or not exit the application.

This is simple in a Console application.

If(Console.ReadLine() == "exit"){
Console.WriteLine("Are you sure you would like to exit?");
If(Console.ReadLine() == "n"){
return;
}
Application.Exit();
}

When it comes to using a richTextBox and a textBox how can I 'Read' the next line the user enters and continue with my if statement, processing the response, just like I would do with a console application?