Inherit from struct
Inheritance isn't alloweded between structs but structs can implement interfaces.
Value types in .NET are weird in that they defined though they are classes derived from a special class called ValueType
. For every value type there is a heap object type which behaves like a class object that derives from ValueType
, but a value-type storage location holds a collection of bytes which either represents a primitive value, or the concatenation of the bytes necessary to hold all of its public and private fields.
Since value type storage locations just hold the bytes necessary to represent their values, and hold neither type information nor any reference to an object which would hold type information, the code which uses a value type storage location must know exactly what it is.
Conventional inheritance requires that objects hold information about their own type, but there is no provision via which value types could do so.
It would be conceptually possible (and useful) for .NET to allow some limited forms of value-type inheritance with some special rules, such that while a BaseStructure
variable could only hold a BaseStructure
and couldn't hold a DerivedStructure
. One could define a StructureUser<T> where T:BaseStructure
, and such class or method could accept any derivative of BaseStructure
and use those members--including fields--which were common to the base type.
Unfortunately, it would be difficult to define rules for generics in such a way as to behave consistently in permitted scenarios and yet not break any existing code.
For example, within a class Foo<T,U> where T:U
it's always possible to store a T
to a variable of type U
, even if U
is a value type (i.e. because value types are sealed, T
and U
are guaranteed to be the same type). If U
could be an inheritable value type and T
could be a derivative, such a guarantee would not hold.
Given the difficulties associated with such inheritance, a more useful alternative would be to provide a safe (even if limited) means via which a property could expose a byref or a const-byref (a byref is the thing which is passed when a parameter uses a ref
qualifier).
Such a feature would remove the unavoidable semantic distinction between fields and properties, and depending upon how it was implemented could offer some major advantages even when used with classes (e.g. it could allow for efficient mixing of immutable and mutable types).
Struct does not support inheritance, if you need you have to use class, see msdn
There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.
A struct Is Implicitly Sealed
According to this link:
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;
}