Nice msdn article here:
The Myth of .NET Purity, Reloaded
Here’s the summary:
Does a solution written for Microsoft .NET have to be 100% .NET? Scott Hanselman looks at how hybrid managed-unmanaged solutions are really the norm.
I tend to agree. You aren’t going to find everything you need written in .NET, so you are going to have to do some thing in the unmanaged space. Fortunately, .NET makes writing unmanaged wrappers pretty painless.