Check if the typeof(object) in a List is a reference type

Question

this seems odd to me:

if(customerList.Count > 0)
{
   if(typeof(customerList[0]).IsReferenceType)
   {
      // do what I want
   }
}

How would you do it?

Answer 1

1. To determine whether the first item in a list is an object of a reference type:

   bool isReferenceType = !(customerList[0] is ValueType);
   

2. To determine whether a list is a List<T> for some T that is a reference type:

   var listType = customerList.GetType();
   if (!listType.IsGeneric || listType.GetGenericTypeDefinition() != typeof(List<>))
       // It’s not a List<T>
       return null;
   return !listType.GetGenericArguments()[0].IsValueType;
   

Answer 2

You are probably trying to determine the actual type of the generic parameter of a generic collection. Like determining at runtime what is a T of a particular List<T>. Do this:

Type collectionType = typeof(customerList);
Type parameterType = collectionType.GetGenericArguments()[0];
bool isReference = !parameterType.IsValueType;