#767 – A struct Is Implicitly Sealed

Every struct in C#, whether it is user-defined or defined in the .NET Framework, is sealed–meaning that you can’t inherit from it.  A struct is sealed because it is a value type and all value types are sealed.

A struct can implement an interface, so it’s possible to see another type name following a colon, after the name of the struct.

In the example below, we get a compile-time error when we try to define a new struct that inherits from the one defined above.

    public struct PersonName
    {
        public PersonName(string first, string last)
        {
            First = first;
            Last = last;
        }

        public string First;
        public string Last;
    }

    // Error at compile time: Type 'PersonName' in interface list is not an interface
    public struct AngryPersonName : PersonName
    {
        public string AngryNickname;
    }