Using is operator with Interface to Generics

Question

I have a few generic classes that implement a common non-generic interface. I create my generic objects and add them to a list. How can I use LINQ, or any other method for that matter, to filter the list by the generic type. I do not need to know T at run-time. I added a type property to the interface and used LINQ to filter by it but I was hoping to use the is operator. Here's a simple example I threw together.

Any Ideas?

interface IOperation
    {
        object GetValue();
    }
    class Add<T> : IOperation
    {
        public object GetValue()
        {
            return 0.0;
        }
    }
    class Multiply<T> : IOperation
    {
        public object GetValue()
        {
            return 0.0;
        }
    }


    private void Form1_Load(object sender, EventArgs e)
    {
        //create some generics referenced by interface
        var operations = new List<IOperation>
        {
            new Add<int>(),
            new Add<double>(),
            new Multiply<int>()
        };

        //how do I use LINQ to find all intances off Add<T> 
        //without specifying T?

        var adds =
            from IOperation op in operations
            where op is Add<> //this line does not compile
            select op;
    }

Answer 1

You can just compare the underlying non-parameterized type names:

var adds =
    from IOperation op in operations
    where op.GetType().Name == typeof(Add<>).Name
    select op;

Note that in the next version of C#, this will be possible due to variance:

var adds =
    from IOperation op in operations
    where op is Add<object>
    select op;