// CS1750: Optional parameter expression of type `null' cannot be converted to parameter type `A' // Line: 8 using System; class GenericClass<T> { public GenericClass (GenericClass<T> g = null, A a = null) { } } class DerivedClass<T> : GenericClass<T> { public DerivedClass (GenericClass<T> g) : base(g) { } } public struct A { public int Field; }