c# - Get property of generic class

Question

I have a generic class, and an object value where obj.GetType().GetGenericTypeDefinition() == typeof(Foo<>).

class Foo<T>
{
    public List<T> Items { get; set; }
}

How do I get the value of Items from obj? Remember, obj is an Object, I can't cast obj as Foo because I don't know what T is.

I was hoping to use reflection for this, but each time I do GetProperty("Items") it returns null. However, if someone knows a good way to do this without reflection, by all means.

Let's say my code looks like this:

//just to demonstrate where this comes from
Foo<int> fooObject = new Foo<int>();
fooObject.Items = someList;
object obj = (object)fooObject;

//now trying to get the Item value back from obj
//assume I have no idea what <T> is
PropertyInfo propInfo = obj.GetType().GetProperty("Items"); //this returns null
object itemValue = propInfo.GetValue(obj, null); //and this breaks because it's null

Answer 1

You should be able to use:

Type t = obj.GetType();

PropertyInfo prop = t.GetProperty("Items");

object list = prop.GetValue(obj);

You will not be able to cast as a List<T> directly, of course, as you don't know the type T, but you should still be able to get the value of Items.

---

Edit:

The following is a complete example, to demonstrate this working:

// Define other methods and classes here
class Foo<T>
{
    public List<T> Items { get; set; }
}

class Program
{
    void Main()
    {   
        //just to demonstrate where this comes from
        Foo<int> fooObject = new Foo<int>();
        fooObject.Items = new List<int> { 1, 2, 3};
        object obj = (object)fooObject;

        //now trying to get the Item value back from obj
        //assume I have no idea what <T> is
        PropertyInfo propInfo = obj.GetType().GetProperty("Items"); //this returns null
        object itemValue = propInfo.GetValue(obj, null);

        Console.WriteLine(itemValue);
                    // Does not print out NULL - prints out System.Collections.Generic.List`1[System.Int32]


        IList values = (IList)itemValue;
        foreach(var val in values)
            Console.WriteLine(val); // Writes out values appropriately
    }
}