Automatic comment via "///" in Visual Studio 2010 above a Delegate

my delegate: I typed over the delegate in VS2010 the 3 slashes "///" and the typical automatic comment开发者_Python百科 appears.

        /// <summary>
        /// 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="?"></typeparam>
        /// <param name="param"></param>
        /// <returns></returns>
        private delegate IEnumerable<T> SearchInputText<T, string>(string param)

Why does it make the 2nd name = "?" ??? should it not be STRING ?

---

Because this code is not compiled:

error CS0081: Type parameter declaration must be an identifier not a type