How to Get a autoindent in a winform TextBox (or RichTextBox) c#

I'm trying to build a very simple text/code editer, and I want to keep the indent from the last line typed. So I need a way to carry over the indent from the last line to this line. For example say I have code like this:

void Method() {
  Console.Write("Test");
}

And I want it to look like this:

void Method() {
  Console.Write("Test");
  next line of code at the same indent level.
}

How can I do this? Code examples would be nice.

Thanks.