How to change AssemblyName after compilation to load as a mod in Unity3d

Question

I have been investigating adding mod support to a Unity3D game. I am new to Unity (but not .NET), so if it seems like I am missing something obvious, please let me know because I probably am. I would like to be able to export objects, including custom scripts, directly from the editor. It is easy enough to get the assembly associated with the script. Any loose scripts in the project seem to get compiled down to Assembly-`CSharp.dll`. The problem comes in when I try to load the assembly at runtime in another Unity project. Calling `Assembly.Load(byte[])` returns to me the assembly of the current project, not the one represented by the byte array. I am assuming this is because the `AssemblyName` of the assembly from the mod project and the host project are both identical (`Assembly-CSharp`, `Version=0.0.0.0`, `Culture=neutral`, `PublicKeyToken=null`). As a test, I updated my Visual Studio project for the mod project, renaming it from Assembly-CSharp to something different. This gets wip…

Accepted Answer

The solution I ended up going with was using Mono.Cecil. Luckily, the Mono.Cecil library is available in the Unity editor, no need to deploy any extra libraries with my mod tools. Mono.Cecil worked great for renaming the assembly after it was compiled. Here is some code I'm using to make it happen:

```
     // Have Mono.Cecil load the assembly
     var assemblyDefinition = Mono.Cecil.AssemblyDefinition.ReadAssembly(assemblyFile.FullName);

// Tell Mono.Cecil to actually change the name
     assemblyDefinition.Name.Name = newAssemblyNameNoExtension;
     assemblyDefinition.MainModule.Name = newAssemblyNameNoExtension;

// We also need to rename any references to project assemblies (first pass assemblies)
     foreach (var reference in assemblyDefinition.MainModule.AssemblyReferences)
     {
        if (Utilities.IsProjectAssembly(reference.Name))
        {
           reference.Name = Utilities.GetModAssemblyName(reference.Name, this._modName);
        }
     }

// Build the new assembly
     byte[] bytes;
     using (var ms = new MemoryStream())
     {
        assemblyDefinition.Write(ms, new Mono.Cecil.WriterParameters() { WriteSymbols = true });
        bytes = ms.ToArray();
     }
```

How to change AssemblyName after compilation to load as a mod in Unity3d

Solution

Problem