CODEWITHSUNDEEP
c#generics
Tarscher
Tarscher

Reputation: 1933

check for generic type

I want to check if a generic variable is of a certain type but don't want to check the generic part.

Let's say I have a variable of List<int> and another of List<double>. I just want to check if it is of type List<>

if(variable is List) {}

And not

if (variable is List<int> || variable is List<double>) {}

is this possible?

Thanks

Upvotes: 3

Views: 1084

Answers (3)

Marc Gravell
Marc Gravell

Reputation: 1062780

You can test an exact type via reflection:

    object list = new List<int>();

    Type type = list.GetType();
    if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(List<>))
    {
        Console.WriteLine("is a List-of-" + type.GetGenericArguments()[0].Name);
    }

Personally, though, I'd look for IList<T> - more versatile than the concrete List<T>:

    foreach (Type interfaceType in type.GetInterfaces())
    {
        if (interfaceType.IsGenericType
            && interfaceType.GetGenericTypeDefinition()
            == typeof(IList<>))
        {
            Console.WriteLine("Is an IList-of-" +
                interfaceType.GetGenericArguments()[0].Name);
        }
    }

Upvotes: 6

Mehrdad Afshari
Mehrdad Afshari

Reputation: 421988

variable.GetType().IsGenericType && 
            variable.GetType().GetGenericTypeDefinition() == typeof(List<>)

Of course, this only works if variable is of type List<T>, and isn't a derived class. If you want to check if it's List<T> or inherited from it, you should traverse the inheritance hierarchy and check the above statement for each base class:

static bool IsList(object obj)
{
    Type t = obj.GetType();
    do {
        if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(List<>))
            return true;
        t = t.BaseType;
    } while (t != null);
    return false;
}

Upvotes: 9

LukeH
LukeH

Reputation: 269368

Type t = variable.GetType();
if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(List<>))
{
    // do something
}

Upvotes: 5

Related Questions