Are there any best practices to call native C++ or Delphi Dlls from C# (ASP.NET)? Is invoking or a COM interop the best way to access those Dlls?
You can use DllImport to achieve your objective, as per the following:
[DllImport("kernel32.dll")]
public static extern IntPtr OpenProcess(uint dwDesiredAccess, bool bInheritHandle, int dwProcessId);
You can use this with any Win32 compatible DLL, including Delphi ones.