1. - This slide is intentionally left blank -
Some of the slides are based on University of Linz .NET presentations.
© University of Linz, Institute for System Software, 2004
published under the Microsoft Curriculum License (

3. TYPE INHERITANCE AWAKENS
FUN WITH C#
EPISODE XIII
TYPE INHERITANCE AWAKENS

4. CLI Type System All types Value types Reference types Pointers
(allocated in-place [with exceptions])
Reference types
(allocated on managed heap)
Pointers
Structures
Enumerations
Classes (e.g. strings)
Interfaces
Arrays
Delegates
Simple types
(Int32, Int64, Double, Boolean, Char, …)
Nullables
User defined structures

5. CLI Type Inheritance pointers (C#: Type *)
System.Object (C# keyword: object)
interfaces (C# keyword: interface)
System.String (C# keyword: string)
System.Array
System.Delegate
arrays (C#: Type[] or Type[,])
System.MulticastDelegate
System.ValueType
delegates (C# keyword: delegate)
user-defined classes (C# keyword: class)
simple types
System.Int32 (C# keyword: int)
System.Double (C# keyword: double)
System.Int64 (C# keyword: long)
System.Enum
System.Nullable (C#: Type?)
user-defined structures (C# keyword: struct)
System.Boolean (C# keyword: bool)
enumerations (C# keyword: enum) …

6. Class System.Object Topmost base class of all other classes
class Object {
protected object MemberwiseClone() {...}
public Type GetType() {...}
public virtual bool Equals (object o) {...}
public virtual string ToString() {...}
public virtual int GetHashCode() {...}
public static bool ReferenceEquals(object objA, object objB); }

7. ValueType.Equals Override

8. CLI Type Inheritance pointers (C#: Type *)
System.Object (C# keyword: object)
interfaces (C# keyword: interface)
System.String (C# keyword: string)
System.Array
System.Delegate
arrays (C#: Type[] or Type[,])
System.MulticastDelegate
System.ValueType
delegates (C# keyword: delegate)
user-defined classes (C# keyword: class)
simple types
System.Int32 (C# keyword: int)
System.Double (C# keyword: double)
System.Int64 (C# keyword: long)
System.Enum
System.Nullable (C#: Type?)
user-defined structures (C# keyword: struct)
System.Boolean (C# keyword: bool)
enumerations (C# keyword: enum) …

9. Ref. Type DOES NOT Imply Instances
pointers (C#: Type *)
System.Object (C# keyword: object)
interfaces (C# keyword: interface)
System.String (C# keyword: string)
System.Array
System.Delegate
arrays (C#: Type[] or Type[,])
System.MulticastDelegate
System.ValueType
delegates (C# keyword: delegate)
user-defined classes (C# keyword: class)
simple types
System.Int32 (C# keyword: int)
System.Double (C# keyword: double)
System.Int64 (C# keyword: long)
System.Enum
System.Nullable (C#: Type?)
user-defined structures (C# keyword: struct)
System.Boolean (C# keyword: bool)
enumerations (C# keyword: enum) …

10. CLI Type Inheritance
pointers (C#: Type *)
System.Object (C# keyword: object)
interfaces (C# keyword: interface)
Interfaces are not inherited from System.Object, but System.Object members are callable/accessible via any interface type expression.
System.String (C# keyword: string)
System.Array
System.Delegate
arrays (C#: Type[] or Type[,])
System.MulticastDelegate
System.ValueType
delegates (C# keyword: delegate)
user-defined classes (C# keyword: class)
simple types
System.Int32 (C# keyword: int)
System.Double (C# keyword: double)
System.Int64 (C# keyword: long)
System.Enum
System.Nullable (C#: Type?)
user-defined structures (C# keyword: struct)
System.Boolean (C# keyword: bool)
enumerations (C# keyword: enum) …

11. CLI Type Inheritance (Sealed Types)
pointers (C#: Type *)
System.Object (C# keyword: object)
interfaces (C# keyword: interface)
System.String (C# keyword: string)
System.Array
System.Delegate
sealed
arrays (C#: Type[] or Type[,])
System.MulticastDelegate
sealed
System.ValueType
delegates (C# keyword: delegate)
user-defined classes (C# keyword: class)
sealed
Optionally sealed
simple types
System.Int32 (C# keyword: int)
System.Double (C# keyword: double)
sealed
System.Int64 (C# keyword: long)
System.Enum
System.Nullable (C#: Type?)
user-defined structures (C# keyword: struct)
sealed
System.Boolean (C# keyword: bool)
sealed
enumerations (C# keyword: enum) …
sealed

12. Hiding Members can be declared as new in a subclass.
They hide inherited members with the same name and signature.
class A {
public int x;
public void F() {...}
public virtual void G() {...} }
class B : A {
public new int x;
public new void F() {...}
public new void G() {...}
B b = new B();
b.x = ...; // accesses B.x
b.F(); ... b.G(); // calls B.F and B.G
((A)b).x = ...; // accesses A.x!
((A)b).F(); ... ((A)b).G(); // calls A.F and A.G!