How to stop Visual Studio from auto formatting certain parts of code?

Are you sure that unchecking:

Options -> Text Editor -> C# -> Formatting -> New Lines -> Place Open Brace on new line for types

doesn't do what you want?

and also uncheck

Place open brace on newline for methods.

(nvrmind.. I see what you are getting at... It is annoying)

AFAIK there is no way to prevent Visual Studio from doing this.