Hi, I want to make a dictionary out of list in a way, that the list becomes keys and values would be empty. I have following code

Dictionary<XmlTest, int?> testBattery =
            new XmlTests().GetRandomTestBattery(id).
                ToDictionary(k => k, v => null);

But I am getting the error "Cannot convert lambda expression to type System.Collections.Generic.IEqualityComparer' because it is not a delegate type"

Any ideas how could I fix it?

(I know I could iterate through and fill the dict one element at a time, but I simply want to use something more elegant)