Mono.Cecilだけでアセンブリをマージする

merge.cs

Action<T> GetAssignMethod<T>(string field, object value)
{
	var arg = Expression.Parameter(typeof(T));
	var body = Expression.Assign(Expression.Field(arg, field), Expression.Constant(value));
	return (Action<T>)Expression.Lambda(typeof(Action<T>), body, arg).Compile();
}
void MoveItems<T>(ICollection<T> src, ICollection<T> dest, Func<T,bool> filter = null)
{
	var items = filter != null ? src.Where(filter).ToList() : src.ToList();
	items.ForEach(x => { src.Remove(x); dest.Add(x); });
}
void VisitTypes(IEnumerable<TypeDefinition> rootset, Action<TypeDefinition> action)
{
	var types = new Stack<TypeDefinition>(rootset);
	while (types.Any())
	{
		var cur = types.Pop();
		action(cur);
		cur.NestedTypes.ForEach(types.Push);
	}
}
void Main()
{
	var src = AssemblyDefinition.ReadAssembly(typeof(MyExtensions).Assembly.Location, new ReaderParameters(ReadingMode.Immediate));
	var dest = AssemblyDefinition.ReadAssembly(@"R:\hoge.exe");

	var src_m = src.MainModule;
	var dest_m = dest.MainModule;

	// ReadingMode.Immediate でも読んでくれないデータを読み込む(MethodDef.Body)
	VisitTypes(src_m.Types, t => t.Methods.ForEach(m => m.Body?.GetHashCode()));

	// モジュール間で乗せ換え（moduleを書き換えないといけないもの）
	var fixmodule = GetAssignMethod<TypeReference>("module", dest_m);
	VisitTypes(src_m.Types, t => t.NestedTypes.ForEach(fixmodule));
	src_m.GetTypeReferences().ForEach(fixmodule);
	
	var nativeTypes =
		from prop in typeof(TypeSystem).GetProperties()
		where prop.PropertyType == typeof(TypeReference)
		select (TypeReference)prop.GetValue(src_m.TypeSystem);
	nativeTypes.ForEach(fixmodule);
	
	// 名前空間の書き換え
	var new_ns = src.Name.Name;
	var oldref = dest_m.AssemblyReferences.First(x => x.FullName == src.FullName);
	dest_m.GetTypeReferences().Where(t => t.Scope == oldref).ForEach(t => t.Namespace = new_ns);
	VisitTypes(src_m.Types, t => t.Namespace = new_ns);

	// モジュール間で乗せ換え（Attach/Detachが必要なもの）
	MoveItems(src_m.AssemblyReferences, dest_m.AssemblyReferences, t => !dest_m.AssemblyReferences.Any(tt => t.FullName == tt.FullName));
	MoveItems(src_m.Types, dest_m.Types, t => !dest_m.Types.Any(tt => t.FullName == tt.FullName));
	MoveItems(src_m.Resources, dest_m.Resources);

	// 旧アセンブリへの参照を自分自身への参照に
	oldref.Name = dest.Name.Name;
	oldref.Version = dest.Name.Version;
	oldref.Culture = dest.Name.Culture;
	oldref.PublicKeyToken = dest.Name.PublicKeyToken;
	
	dest.Write(@"r:\dest.exe");
}