System.Object Class

Supports all classes in the .NET Framework class hierarchy and provides low-level services to derived classes. This is the ultimate base class of all classes in the .NET Framework; it is the root of the type hierarchy.

See Also: Object


public class Object


Languages typically do not require a class to declare inheritance from Object because the inheritance is implicit.

Because all classes in the .NET Framework are derived from Object, every method defined in the Object class is available in all objects in the system. Derived classes can and do override some of these methods, including:

  • Object.Equals(Object) - Supports comparisons between objects.

  • Object.Finalize - Performs cleanup operations before an object is automatically reclaimed.

  • Object.GetHashCode - Generates a number corresponding to the value of the object to support the use of a hash table.

  • Object.ToString - Manufactures a human-readable text string that describes an instance of the class.

Performance Considerations

If you are designing a class, such as a collection, that must handle any type of object, you can create class members that accept instances of the Object class. However, the process of boxing and unboxing a type carries a performance cost. If you know your new class will frequently handle certain value types you can use one of two tactics to minimize the cost of boxing.

  • Create a general method that accepts an Object type, and a set of type-specific method overloads that accept each value type you expect your class to frequently handle. If a type-specific method exists that accepts the calling parameter type, no boxing occurs and the type-specific method is invoked. If there is no method argument that matches the calling parameter type, the parameter is boxed and the general method is invoked.

  • Design your type and its members to use generics. The common language runtime creates a closed generic type when you create an instance of your class and specify a generic type argument. The generic method is type-specific and can be invoked without boxing the calling parameter.

Although it is sometimes necessary to develop general purpose classes that accept and return Object types, you can improve performance by also providing a type-specific class to handle a frequently used type. For example, providing a class that is specific to setting and getting Boolean values eliminates the cost of boxing and unboxing Boolean values.

Thread Safety

All public static members of this type are safe for multithreaded operations. No instance members are guaranteed to be thread safe.


Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0,,

The members of System.Object are listed below.

Public Constructors

Initializes a new instance of the Object class.

Public Methods

Equals(Object) : Boolean

Determines whether the specified object is equal to the current object.

Equals(Object, Object) : Boolean

Determines whether the specified object instances are considered equal.


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.

GetHashCode() : Int32

Serves as the default hash function.

GetType() : Type

Gets the Type of the current instance.

ReferenceEquals(Object, Object) : Boolean

Determines whether the specified Object instances are the same instance.

ToString() : String

Returns a string that represents the current object.

Protected Methods

MemberwiseClone() : Object

Creates a shallow copy of the current Object.