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.NET Framework Class Library

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.

To browse the .NET Framework source code for this type, see the Reference Source.

System.Object
  All classes, structures, enumerations, and delegates.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
<ClassInterfaceAttribute(ClassInterfaceType.AutoDual)> _
Public Class Object

The Object type exposes the following members.

  Name Description
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps Object Initializes a new instance of the Object class.
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  Name Description
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps Equals(Object) Determines whether the specified object is equal to the current object.
Public method Static member Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps Equals(Object, Object) Determines whether the specified object instances are considered equal.
Protected method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps GetHashCode Serves as the default hash function.
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps GetType Gets the Type of the current instance.
Protected method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps MemberwiseClone Creates a shallow copy of the current Object.
Public method Static member Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps ReferenceEquals Determines whether the specified Object instances are the same instance.
Public method Supported by the XNA Framework Supported by Portable Class Library Supported in .NET for Windows Store apps ToString Returns a string that represents the current object.
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Note Note

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

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:

  • Equals - Supports comparisons between objects.

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

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

  • 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.

The following example defines a Point type derived from the Object class and overrides many of the virtual methods of the Object class. In addition, the example shows how to call many of the static and instance methods of the Object class.

' The Point class is derived from System.Object. 
Class Point
    Public x, y As Integer 

    Public Sub New(ByVal x As Integer, ByVal y As Integer) 
        Me.x = x
        Me.y = y
    End Sub 

    Public Overrides Function Equals(ByVal obj As Object) As Boolean  
        ' If Me and obj do not refer to the same type, then they are not equal. 
        Dim objType As Type = obj.GetType()
        Dim meType  As Type = Me.GetType()
        If Not objType.Equals(meType) Then 
            Return False 
        End If  
        ' Return true if  x and y fields match. 
        Dim other As Point = CType(obj, Point)
        Return Me.x = other.x AndAlso Me.y = other.y
    End Function  

    ' Return the XOR of the x and y fields. 
    Public Overrides Function GetHashCode() As Integer  
        Return (x << 1) XOr y
    End Function  

    ' Return the point's value as a string. 
    Public Overrides Function ToString() As String  
        Return String.Format("({0}, {1})", x, y)
    End Function 

    ' Return a copy of this point object by making a simple field copy. 
    Public Function Copy() As Point 
        Return CType(Me.MemberwiseClone(), Point)
    End Function 
End Class   

NotInheritable Public Class App
    Shared Sub Main() 
        ' Construct a Point object. 
        Dim p1 As New Point(1, 2)

        ' Make another Point object that is a copy of the first. 
        Dim p2 As Point = p1.Copy()

        ' Make another variable that references the first Point object. 
        Dim p3 As Point = p1

        ' The line below displays false because p1 and p2 refer to two different objects.
        Console.WriteLine([Object].ReferenceEquals(p1, p2))

        ' The line below displays true because p1 and p2 refer to two different objects  
        ' that have the same value.
        Console.WriteLine([Object].Equals(p1, p2))

        ' The line below displays true because p1 and p3 refer to one object.
        Console.WriteLine([Object].ReferenceEquals(p1, p3))

        ' The line below displays: p1's value is: (1, 2)
        Console.WriteLine("p1's value is: {0}", p1.ToString())

    End Sub 
End Class 
' This example produces the following output: 

' False 
' True 
' True 
' p1's value is: (1, 2) 
'

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Public static (Shared in Visual Basic) members of this type are thread safe. Instance members are not guaranteed to be thread-safe.