Call unmanaged class in C#

[nebulom]

I need help with calling an unmanaged class in my C# code. Let's say I have a SomeClass.SomeFunction. How do I call the SomeFunction method via DLLImport? I have something like

[DllImport("Some.dll", EntryPoint = "SomeClass.SomeFunction", CallingConvention = CallingConvention.StdCall)]
		public static extern string SomeFunction();

but it says

System.EntryPointNotFoundException : Unable to find an entry point named 'SomeClass.SomeFunctio' in DLL 'Some.dll'...