Object Class

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Source:

Object.cs

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

public ref class System::Object

public class Object

type obj = class

Public Class Object

Examples

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.

using System;

// The Point class is derived from System.Object.
class Point
{
    public int x, y;

    public Point(int x, int y)
    {
        this.x = x;
        this.y = y;
    }

    public override bool Equals(object obj)
    {
        // If this and obj do not refer to the same type, then they are not equal.
        if (obj.GetType() != this.GetType()) return false;

        // Return true if  x and y fields match.
        var other = (Point) obj;
        return (this.x == other.x) && (this.y == other.y);
    }

    // Return the XOR of the x and y fields.
    public override int GetHashCode()
    {
        return x ^ y;
    }

    // Return the point's value as a string.
    public override String ToString()
    {
        return $"({x}, {y})";
    }

    // Return a copy of this point object by making a simple field copy.
    public Point Copy()
    {
        return (Point) this.MemberwiseClone();
    }
}

public sealed class App
{
    static void Main()
    {
        // Construct a Point object.
        var p1 = new Point(1,2);

        // Make another Point object that is a copy of the first.
        var p2 = p1.Copy();

        // Make another variable that references the first Point object.
        var p3 = 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: {p1.ToString()}");
    }
}

// This code example produces the following output:
//
// False
// True
// True
// p1's value is: (1, 2)
//

open System

// The Point class is derived from System.Object.
type Point(x, y) =
    member _.X = x
    member _.Y = y
    override _.Equals obj =
        // If this and obj do not refer to the same type, then they are not equal.
        match obj with
        | :? Point as other ->
            // Return true if  x and y fields match.
            x = other.X &&  y = other.Y
        | _ -> 
            false

    // Return the XOR of the x and y fields.
    override _.GetHashCode() =
        x ^^^ y

    // Return the point's value as a string.
    override _.ToString() =
        $"({x}, {y})"

    // Return a copy of this point object by making a simple field copy.
    member this.Copy() =
        this.MemberwiseClone() :?> Point

// Construct a Point object.
let p1 = Point(1,2)

// Make another Point object that is a copy of the first.
let p2 = p1.Copy()

// Make another variable that references the first Point object.
let p3 = p1

// The line below displays false because p1 and p2 refer to two different objects.
printfn $"{Object.ReferenceEquals(p1, p2)}"

// The line below displays true because p1 and p2 refer to two different objects that have the same value.
printfn $"{Object.Equals(p1, p2)}"

// The line below displays true because p1 and p3 refer to one object.
printfn $"{Object.ReferenceEquals(p1, p3)}"

// The line below displays: p1's value is: (1, 2)
printfn $"p1's value is: {p1.ToString()}"
// This code example produces the following output:
//
// False
// True
// True
// p1's value is: (1, 2)
//

using namespace System;

// The Point class is derived from System.Object.
ref class Point
{
public:
    int x;
public:
    int y;

public:
    Point(int x, int y)
    {
        this->x = x;
        this->y = y;
    }

public:
    virtual bool Equals(Object^ obj) override
    {
        // If this and obj do not refer to the same type,
        // then they are not equal.
        if (obj->GetType() != this->GetType())
        {
            return false;
        }

        // Return true if  x and y fields match.
        Point^ other = (Point^) obj;
        return (this->x == other->x) && (this->y == other->y);
    }

    // Return the XOR of the x and y fields.
public:
    virtual int GetHashCode() override 
    {
        return x ^ y;
    }

    // Return the point's value as a string.
public:
    virtual String^ ToString() override 
    {
        return String::Format("({0}, {1})", x, y);
    }

    // Return a copy of this point object by making a simple
    // field copy.
public:
    Point^ Copy()
    {
        return (Point^) this->MemberwiseClone();
    }
};

int main()
{
    // Construct a Point object.
    Point^ p1 = gcnew Point(1, 2);

    // Make another Point object that is a copy of the first.
    Point^ p2 = p1->Copy();

    // Make another variable that references the first
    // Point object.
    Point^ p3 = 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());
}

// This code produces the following output.
//
// False
// True
// True
// p1's value is: (1, 2)

' 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 $"({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: {p1.ToString()}")
    
    End Sub
End Class
' This example produces the following output:
'
' False
' True
' True
' p1's value is: (1, 2)
'

Remarks

For more information about this API, see Supplemental API remarks for Object.

Constructors

Object()

Initializes a new instance of the Object class.

Methods

Equals(Object, Object)	Determines whether the specified object instances are considered equal.
Equals(Object)	Determines whether the specified object is equal to the current object.
Finalize()	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.
GetHashCode()	Serves as the default hash function.
GetType()	Gets the Type of the current instance.
MemberwiseClone()	Creates a shallow copy of the current Object.
ReferenceEquals(Object, Object)	Determines whether the specified Object instances are the same instance.
ToString()	Returns a string that represents the current object.

Thread Safety

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