Question

This may be a basic question, but I googled it and didn’t find an answer. I hope you will help me. Consider I have an enum ContactNumberType:

string[] names = Enum.GetNames(typeof(ContactNumberType))

If I use the above, the compiler gives no error, but when I write:

string[] names = Enum.GetNames(ContactNumberType)

It says:

ContactNumberType is a type but used like a variable.

While the type of ContactNumberType is Enum, as far as I know, and the argument of method GetNames needs EnumType, so whats the issue with that?

Answer 1

You have to use typeof becuase the GetNames() method takes a parameter of type Type. Keep in mind that providing a type name is not the same as an instance of Type, which is an object that contains the details of that type.

To pass a type as a parameter, you have two basic choices:

• Pass a Type instance
• Use a generic

The first of these (which many older methods such as Enum.GetNames() does) requires you to get a Type instance from the type identifier, which we can do using the typeof() operator.

The second of these allows you to pass a type name as a parameter to a method or class to make that method or class generic and tends to be used on newer methods (generics were introduced in .NET 2.0):

var items = someList.OfType<SomeTypeName>();

Enum, however, doesn’t have a generic form of GetNames() that allows this, though you could create something like one:

public static class EnumHelper
{
    public static string[] GetNames<T>() where T : struct
    {
        return Enum.GetNames(typeof(T))
    }
}

Which you could then call like:

string[] names = EnumHelper.GetNames<ContactNumberType>();