Get property of generic class

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
    }
}

@ReedCopsey is absolutely correct, but in case you're really asking the question "How do I fish out the generic details of a type?", here's some "Fun with Reflection":

public void WhatsaFoo(object obj)
{
    var genericType = obj.GetType().GetGenericTypeDefinition();
    if(genericType == typeof(Foo<>))
    {
        // Figure out what generic args were used to make this thing
        var genArgs = obj.GetType().GetGenericArguments();

        // fetch the actual typed variant of Foo
        var typedVariant = genericType.MakeGenericType(genArgs);

        // alternatively, we can say what the type of T is...
        var typeofT = obj.GetType().GetGenericArguments().First();

        // or fetch the list...
        var itemsOf = typedVariant.GetProperty("Items").GetValue(obj, null);
    }
}

Something like this should do the trick:

var foo = new Foo<int>();
foo.Items = new List<int>(new int[]{1,2,3});

// this check is probably not needed, but safety first :)
if (foo.GetType().GetProperties().Any(p => p.Name == "Items"))
{
    var items = foo.GetType().GetProperty("Items").GetValue(foo, null);
}