In the upcoming SharpDevelop 3 there's a new refactoring included: Extract method. With it you can easily split a method into two independent methods.

If you want to use it you first have to select the piece of code you want to extract:

Then just click on Refactor > Extract method in the main menu:

 The preview will pop up, here you can enter a name for the new method:

 After entering a name click "OK" and here you can see the new method and the inserted call:

Of course you can undo the change, just press Ctrl+Z.

I hope you find this refactoring useful and I would be glad to receive any comments on this.