How can I add a field to an Enum?

[untold-titan]

I'm trying to write a mod for a unity game, and I'm using cecil to edit the main assembly of the game.

This is the code I'm using:

var module = assembly.MainModule;
var itemType = module.GetType("EItemType");

var TestInjectedItem = new FieldDefinition("InjectedItem", FieldAttributes.Public | FieldAttributes.Static | FieldAttributes.Literal, itemType) { Constant = 114 };
itemType.Fields.Add(TestInjectedItem);

// Overwrite the assembly in the game files hehehe
assembly.Write();

I have double checked using dotPeek to make sure that 114 is a valid constant value (eg incrementing the previous ones)

This is the class I'm editing:

public enum EItemType
{
  None = -1, 
  BasicCardPack = 0,
  BasicCardBox = 1,
//...
  PlayMat16 = 110, 
  PlayMat17 = 111,
  PlayMat18 = 112, 
  Max = 113,
}

[Serg046]

Your code should work (however, you might want to add FieldAttributes.HasDefault)

var asmDef = AssemblyDefinition.ReadAssembly(typeof(EItemType).Module.FullyQualifiedName);
var module = asmDef.MainModule;
var itemType = module.GetType(nameof(EItemType));
var TestInjectedItem = new FieldDefinition("InjectedItem", FieldAttributes.Public | FieldAttributes.Static | FieldAttributes.Literal, itemType) { Constant = 114 };
itemType.Fields.Add(TestInjectedItem);
using var stream = new MemoryStream();
asmDef.Write(stream);
var newAsm = Assembly.Load(stream.ToArray());
var newType = newAsm.GetType(nameof(EItemType));

Console.WriteLine("Old type fields");
PrintFields(typeof(EItemType));
Console.WriteLine();
Console.WriteLine("New type fields");
PrintFields(newType);

//--------------------------------------------------------

void PrintFields(Type type)
{
	foreach (var field in type.GetFields())
	{
		Console.WriteLine(field.Name);
	}
}

public enum EItemType
{
    None = -1, 
    BasicCardPack = 0
}

Code sample above prints the following:

Old type fields
value__
None
BasicCardPack

New type fields
value__
None
BasicCardPack
InjectedItem

You can run it and see https://dotnetfiddle.net/yBwEvd