Why the following two methods generating the same IL?
public static class Extensions
{
public static T Include<T>(this System.Enum type,T value) where T:struct
{
return ((T) (ValueType) (((int) (ValueType) type | (int) (ValueType) value)));
}
public static T Include1<T>(this System.Enum type, T value)
{
return ((T)(object)((int)(object)type | (int)(object)value));
}
}
If you see the IL generated for these two methods they look the same or am i missing something... why boxing is happening for开发者_开发知识库 the first Include method?
ValueType
is a reference-type. Honest. It is only a struct when it is T
. You would need to replace all the ValueType
with T
for it not to box. However, there will be no inbuilt cast from T
to int
... so: you can't. You will have to box. Plus, not all enums are int
-based (your box-as-enum, unbox-as-int will fail for a enum Foo : ushort
, for example).
In C# 4.0, dynamic
might be a cheeky way to do this:
public static T Include<T>(this T type, T value) where T : struct
{
return ((dynamic)type) | value;
}
Otherwise, some meta-programming (essentially to do what dynamic
does, but manually):
static void Main()
{
var both = Test.A.Include(Test.B);
}
enum Test : ulong
{
A = 1, B = 2
}
public static T Include<T>(this T type, T value) where T : struct
{
return DynamicCache<T>.or(type, value);
}
static class DynamicCache<T>
{
public static readonly Func<T, T, T> or;
static DynamicCache()
{
if(!typeof(T).IsEnum) throw new InvalidOperationException(typeof(T).Name + " is not an enum");
var dm = new DynamicMethod(typeof(T).Name + "_or", typeof(T), new Type[] { typeof(T), typeof(T) }, typeof(T),true);
var il = dm.GetILGenerator();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Or);
il.Emit(OpCodes.Ret);
or = (Func<T, T, T>)dm.CreateDelegate(typeof(Func<T, T, T>));
}
}
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