There's a great new reference on MSDN that makes attempt to map Win32 API to their .NET Framework equivalent. So if you're having trouble making a certain translation, or would like to avoid a p/invoke here or there, this is a pretty long list that might help you out:

Microsoft Win32 to Microsoft .NET Framework API Map

One thing to note is that the translation from Win32 to .NET does assume “same app”, not that you are manipulating an external app. For example, the translation for SetParent is System.Windows.Forms.Form.Parent. That is great assuming that the window you're setting the parent of is part of your own app etc. There's some things missing too - but those seem to be in cases where there is no .NET counter-part for the Win32 API (or does not translate well)