How to determine whether T is a value type or reference class in generic?

I have a generic method behavior of which depends on T is reference type or value type. It looks so:

T SomeGenericMethod <T> (T obj)
{
  if (T is class) //What condition I must write in the brackets?
   //to do one stuff
  else //if T is a value type like struct, int, enum and etc.
   //to do another stuff
}

I can't duplicate this method like:

T SomeGenericMethod <T> (T obj) where T : class
{
 //Do one stuff
}

T SomeGenericMethod <T> (T obj) where T : struct
{
 //Do another stuff
}

because their signatures are equal. Can anyone help me?

You can use the typeof operator with generic types, so typeof(T) will get the Type reference corresponding to T, and then use the IsValueType property:

if (typeof(T).IsValueType)

Or if you want to include nullable value types as if they were reference types:

// Only true if T is a reference type or nullable value type
if (default(T) == null)

[The following answer does not check the static type of T but the dynamic type of obj. This is not exactly what you asked for, but since it might be useful for your problem anyway, I'll keep this answer for reference.]

All value types (and only those) derive from System.ValueType. Thus, the following condition can be used:

if (obj is ValueType) {
    ...
} else {
    ...
}

Type.IsValueType tells, naturally, if Type is a value type. Hence, typeof(T).IsValueType.

try this:

if (typeof(T).IsValueType)

I'm late to the party, but I just stumbled on this. So as of determining if it's a Reference-Type,

typeof(T).IsClass

respectively

obj.GetType().IsClass

could work (.net 4.7+ , not checked on former Versions)