Everything Ultimately Derives from System.Object -CodeIdol

Everything Ultimately Derives from `System.Object`

Given any object, whether a custom class or one built into the system, the methods shown in Figure will be defined.

Figure Members of `System.Object`
Method Name	Description
`public virtual bool` `Equals(object o)`	Returns true if the object supplied as a parameter is equal in value, not necessarily in reference, to the instance.
`public virtual int` `GetHashCode()`	Returns an integer corresponding to an evenly spread hash code. This is useful for collections such as `HashTable` collections.
`public` `Type GetType()`	Returns an object of type `System.Type` corresponding to the type of the object instance.
`public static bool` `ReferenceEquals(object` `a,object` `b)`	Returns true if the two supplied parameters refer to the same object.
`public virtual string` `ToString()`	Returns a string representation of the object instance.
`public virtual void` `Finalize()`	An alias for the destructor; informs the object to prepare for termination. C# prevents calling this method directly.
`protected object` `MemberwiseClone()`	Clones the object in question by performing a shallow copy; references are copied, but not the data within a referenced type.

All of these methods appear on all objects through inheritance; all objects derive (either directly or via an inheritance chain) from object. Even literals include these methods, enabling somewhat peculiar-looking code like this:

Console.WriteLine( 42.ToString() );

Again, everything derives from object , even class definitions that don't have any explicit derivation. The two declarations for PdaItem in Listing 6.21, therefore, result in identical CIL.

Listing 6.21. `System.Object` Derivation Implied When No Derivation Is Specified Explicitly

public class PdaItem
{
  // ...
}
___________________________________________________________________________
___________________________________________________________________________
public class PdaItem : object
{
  // ...
}

When the object's default implementation isn't sufficient, programmers can override one or more of the three virtual methods. Chapter 9 describes the details for doing this.

Feb. 13, 2011, 4:24 a.m.
posted by tekkero

Everything Ultimately Derives from System.Object