This is one of those problems that I couldn’t find the answer with google.
Trying to load a C++ mixed mode assembly (like a CLR class library) from a byte array instead of a file throws a FileLoadException.
// ClassLib.dll is a mixed-mode assembly (from a C++ CLR Class Library project
Assembly.Load("ClassLib"); // Works
using (var stream = new FileStream("ClassLib.dll", FileMode.Open, FileAccess.Read))
var bytes = new byte[stream.Length];
stream.Read(bytes, 0, bytes.Length);
Assembly.Load(bytes); // System.IO.FileLoadException "Unverifiable code failed policy check. (Exception from HRESULT: 0x80131402)"