# Object.EqualsObject.EqualsObject.EqualsObject.Equals Method

## 定義

2 つのオブジェクト インスタンスが等しいかどうかを判断します。Determines whether two object instances are equal.

## オーバーロード

 Equals(Object) Equals(Object) Equals(Object) Equals(Object) 指定したオブジェクトが、現在のオブジェクトと等しいかどうかを判断します。Determines whether the specified object is equal to the current object. Equals(Object, Object) Equals(Object, Object) Equals(Object, Object) Equals(Object, Object) 指定されたインスタンスが等しいかどうかを判断します。Determines whether the specified object instances are considered equal.

## Equals(Object)Equals(Object)Equals(Object)Equals(Object)

``````public:
virtual bool Equals(System::Object ^ obj);``````
``public virtual bool Equals (object obj);``
``````abstract member Equals : obj -> bool
override this.Equals : obj -> bool``````
``Public Overridable Function Equals (obj As Object) As Boolean``

#### パラメーター

obj
Object Object Object Object

### 例

``````using System;

class Point
{
protected int x, y;

public Point() : this(0, 0)
{ }

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

public override bool Equals(Object obj)
{
//Check for null and compare run-time types.
if ((obj == null) || ! this.GetType().Equals(obj.GetType()))
{
return false;
}
else {
Point p = (Point) obj;
return (x == p.x) && (y == p.y);
}
}

public override int GetHashCode()
{
return (x << 2) ^ y;
}

public override string ToString()
{
return String.Format("Point({0}, {1})", x, y);
}
}

sealed class Point3D: Point
{
int z;

public Point3D(int x, int y, int z) : base(x, y)
{
this.z = z;
}

public override bool Equals(Object obj)
{
Point3D pt3 = obj as Point3D;
if (pt3 == null)
return false;
else
return base.Equals((Point)obj) && z == pt3.z;
}

public override int GetHashCode()
{
return (base.GetHashCode() << 2) ^ z;
}

public override String ToString()
{
return String.Format("Point({0}, {1}, {2})", x, y, z);
}
}

class Example
{
public static void Main()
{
Point point2D = new Point(5, 5);
Point3D point3Da = new Point3D(5, 5, 2);
Point3D point3Db = new Point3D(5, 5, 2);
Point3D point3Dc = new Point3D(5, 5, -1);

Console.WriteLine("{0} = {1}: {2}",
point2D, point3Da, point2D.Equals(point3Da));
Console.WriteLine("{0} = {1}: {2}",
point2D, point3Db, point2D.Equals(point3Db));
Console.WriteLine("{0} = {1}: {2}",
point3Da, point3Db, point3Da.Equals(point3Db));
Console.WriteLine("{0} = {1}: {2}",
point3Da, point3Dc, point3Da.Equals(point3Dc));
}
}
// The example displays the following output:
//       Point(5, 5) = Point(5, 5, 2): False
//       Point(5, 5) = Point(5, 5, 2): False
//       Point(5, 5, 2) = Point(5, 5, 2): True
//       Point(5, 5, 2) = Point(5, 5, -1): False
``````
``````Class Point
Protected x, y As Integer

Public Sub New()
Me.x = 0
Me.y = 0
End Sub

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

Public Overrides Function Equals(obj As Object) As Boolean
' Check for null and compare run-time types.
If obj Is Nothing OrElse Not Me.GetType().Equals(obj.GetType()) Then
Return False
Else
Dim p As Point = DirectCast(obj, Point)
Return x = p.x AndAlso y = p.y
End If
End Function

Public Overrides Function GetHashCode() As Integer
Return (x << 2) XOr y
End Function

Public Overrides Function ToString() As String
Return String.Format("Point({0}, {1})", x, y)
End Function
End Class

Class Point3D : Inherits Point
Private z As Integer

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

Public Overrides Function Equals(ByVal obj As Object) As Boolean
Dim pt3 As Point3D = TryCast(obj, Point3D)
If pt3 Is Nothing Then
Return False
Else
Return MyBase.Equals(CType(pt3, Point)) AndAlso z = pt3.Z
End If
End Function

Public Overrides Function GetHashCode() As Integer
Return (MyBase.GetHashCode() << 2) XOr z
End Function

Public Overrides Function ToString() As String
Return String.Format("Point({0}, {1}, {2})", x, y, z)
End Function
End Class

Module Example
Public Sub Main()
Dim point2D As New Point(5, 5)
Dim point3Da As New Point3D(5, 5, 2)
Dim point3Db As New Point3D(5, 5, 2)
Dim point3Dc As New Point3D(5, 5, -1)

Console.WriteLine("{0} = {1}: {2}",
point2D, point3Da, point2D.Equals(point3Da))
Console.WriteLine("{0} = {1}: {2}",
point2D, point3Db, point2D.Equals(point3Db))
Console.WriteLine("{0} = {1}: {2}",
point3Da, point3Db, point3Da.Equals(point3Db))
Console.WriteLine("{0} = {1}: {2}",
point3Da, point3Dc, point3Da.Equals(point3Dc))
End Sub
End Module
' The example displays the following output
'       Point(5, 5) = Point(5, 5, 2): False
'       Point(5, 5) = Point(5, 5, 2): False
'       Point(5, 5, 2) = Point(5, 5, 2): True
'       Point(5, 5, 2) = Point(5, 5, -1): False
``````

`Point.Equals`ことを確認する方法を確認します、`obj`引数がないnullこのオブジェクトと同じ型のインスタンスを参照しているとします。The `Point.Equals` method checks to make sure that the `obj` argument is not null and that it references an instance of the same type as this object. かどうか、いずれかのチェックが失敗した、メソッドを返します`false`します。If either check fails, the method returns `false`.

`Point.Equals`メソッドの呼び出し、GetTypeする 2 つのオブジェクトのランタイム型が同じであるかどうかを判断するメソッド。The `Point.Equals` method calls the GetType method to determine whether the run-time types of the two objects are identical. メソッドは、フォームのチェックを使用する場合`obj is Point`(C#) または`TryCast(obj, Point)`Visual Basic の場合、チェックは返して`true`の場合、`obj`の派生クラスのインスタンスは、`Point`場合でも、`obj`と現在インスタンスは、同じ実行時の型のではありません。If the method used a check of the form `obj is Point` in C# or `TryCast(obj, Point)` in Visual Basic, the check would return `true` in cases where `obj` is an instance of a derived class of `Point`, even though `obj` and the current instance are not of the same run-time type. 両方のオブジェクトが同じ型、メソッドのキャストのあることを確認したら`obj`入力`Point`し、2 つのオブジェクトのインスタンス フィールドを比較した結果を返します。Having verified that both objects are of the same type, the method casts `obj` to type `Point` and returns the result of comparing the instance fields of the two objects.

`Point3D.Equals`、継承した`Point.Equals`メソッドをオーバーライドObject.Equals(Object)が、何を行う前に呼び出されます。In `Point3D.Equals`, the inherited `Point.Equals` method, which overrides Object.Equals(Object), is invoked before anything else is done. `Point3D`シール クラスは、(`NotInheritable` Visual Basic で)、チェックイン フォーム`obj is Point`(C#) または`TryCast(obj, Point)`Visual Basic では、ことを確認するための適切な`obj`は、`Point3D`オブジェクト。Because `Point3D` is a sealed class (`NotInheritable` in Visual Basic), a check in the form `obj is Point` in C# or `TryCast(obj, Point)` in Visual Basic is adequate to ensure that `obj` is a `Point3D` object. ある場合、`Point3D`オブジェクトにキャストされた、`Point`オブジェクトし、の基本クラスの実装に渡されるEqualsします。If it is a `Point3D` object, it is cast to a `Point` object and passed to the base class implementation of Equals. 場合にのみ、継承された`Point.Equals`メソッドを返します。`true`メソッドの比較には、`z`インスタンス フィールドを、派生クラスで導入されました。Only when the inherited `Point.Equals` method returns `true` does the method compare the `z` instance fields introduced in the derived class.

``````using System;

class Rectangle
{
private Point a, b;

public Rectangle(int upLeftX, int upLeftY, int downRightX, int downRightY)
{
this.a = new Point(upLeftX, upLeftY);
this.b = new Point(downRightX, downRightY);
}

public override bool Equals(Object obj)
{
// Perform an equality check on two rectangles (Point object pairs).
if (obj == null || GetType() != obj.GetType())
return false;
Rectangle r = (Rectangle)obj;
return a.Equals(r.a) && b.Equals(r.b);
}

public override int GetHashCode()
{
return Tuple.Create(a, b).GetHashCode();
}

public override String ToString()
{
return String.Format("Rectangle({0}, {1}, {2}, {3})",
a.x, a.y, b.x, b.y);
}
}

class Point
{
internal int x;
internal int y;

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

public override bool Equals (Object obj)
{
// Performs an equality check on two points (integer pairs).
if (obj == null || GetType() != obj.GetType()) return false;
Point p = (Point)obj;
return (x == p.x) && (y == p.y);
}

public override int GetHashCode()
{
return Tuple.Create(x, y).GetHashCode();
}
}

class Example
{
public static void Main()
{
Rectangle r1 = new Rectangle(0, 0, 100, 200);
Rectangle r2 = new Rectangle(0, 0, 100, 200);
Rectangle r3 = new Rectangle(0, 0, 150, 200);

Console.WriteLine("{0} = {1}: {2}", r1, r2, r1.Equals(r2));
Console.WriteLine("{0} = {1}: {2}", r1, r3, r1.Equals(r3));
Console.WriteLine("{0} = {1}: {2}", r2, r3, r2.Equals(r3));
}
}
// The example displays the following output:
//    Rectangle(0, 0, 100, 200) = Rectangle(0, 0, 100, 200): True
//    Rectangle(0, 0, 100, 200) = Rectangle(0, 0, 150, 200): False
//    Rectangle(0, 0, 100, 200) = Rectangle(0, 0, 150, 200): False
``````
``````Class Rectangle
Private a, b As Point

Public Sub New(ByVal upLeftX As Integer, ByVal upLeftY As Integer, _
ByVal downRightX As Integer, ByVal downRightY As Integer)
Me.a = New Point(upLeftX, upLeftY)
Me.b = New Point(downRightX, downRightY)
End Sub

Public Overrides Function Equals(ByVal obj As [Object]) As Boolean
' Performs an equality check on two rectangles (Point object pairs).
If obj Is Nothing OrElse Not [GetType]().Equals(obj.GetType()) Then
Return False
End If
Dim r As Rectangle = CType(obj, Rectangle)
Return a.Equals(r.a) AndAlso b.Equals(r.b)
End Function

Public Overrides Function GetHashCode() As Integer
Return Tuple.Create(a, b).GetHashCode()
End Function

Public Overrides Function ToString() As String
Return String.Format("Rectangle({0}, {1}, {2}, {3})",
a.x, a.y, b.x, b.y)
End Function
End Class

Class Point
Friend x As Integer
Friend 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
' Performs an equality check on two points (integer pairs).
If obj Is Nothing OrElse Not [GetType]().Equals(obj.GetType()) Then
Return False
Else
Dim p As Point = CType(obj, Point)
Return x = p.x AndAlso y = p.y
End If
End Function

Public Overrides Function GetHashCode() As Integer
Return Tuple.Create(x, y).GetHashCode()
End Function
End Class

Class Example
Public Shared Sub Main()
Dim r1 As New Rectangle(0, 0, 100, 200)
Dim r2 As New Rectangle(0, 0, 100, 200)
Dim r3 As New Rectangle(0, 0, 150, 200)

Console.WriteLine("{0} = {1}: {2}", r1, r2, r1.Equals(r2))
Console.WriteLine("{0} = {1}: {2}", r1, r3, r1.Equals(r3))
Console.WriteLine("{0} = {1}: {2}", r2, r3, r2.Equals(r3))
End Sub
End Class
' The example displays the following output:
'    Rectangle(0, 0, 100, 200) = Rectangle(0, 0, 100, 200): True
'    Rectangle(0, 0, 100, 200) = Rectangle(0, 0, 150, 200): False
'    Rectangle(0, 0, 100, 200) = Rectangle(0, 0, 150, 200): False
``````

C# および Visual Basic などの一部の言語では、演算子のオーバー ロードをサポートします。Some languages such as C# and Visual Basic support operator overloading. オーバーライドする必要がありますも、型は、等値演算子をオーバー ロード、ときに、Equals(Object)同じ機能を提供するメソッド。When a type overloads the equality operator, it must also override the Equals(Object) method to provide the same functionality. 記述することでこれは通常、Equals(Object)メソッドに関して次の例のように、オーバー ロードされた等値演算子。This is typically accomplished by writing the Equals(Object) method in terms of the overloaded equality operator, as in the following example.

``````using System;

public struct Complex
{
public double re, im;

public override bool Equals(Object obj)
{
return obj is Complex && this == (Complex)obj;
}

public override int GetHashCode()
{
return Tuple.Create(re, im).GetHashCode();
}

public static bool operator ==(Complex x, Complex y)
{
return x.re == y.re && x.im == y.im;
}

public static bool operator !=(Complex x, Complex y)
{
return !(x == y);
}

public override String ToString()
{
return String.Format("({0}, {1})", re, im);
}
}

class MyClass
{
public static void Main()
{
Complex cmplx1, cmplx2;

cmplx1.re = 4.0;
cmplx1.im = 1.0;

cmplx2.re = 2.0;
cmplx2.im = 1.0;

Console.WriteLine("{0} <> {1}: {2}", cmplx1, cmplx2, cmplx1 != cmplx2);
Console.WriteLine("{0} = {1}: {2}", cmplx1, cmplx2, cmplx1.Equals(cmplx2));

cmplx2.re = 4.0;

Console.WriteLine("{0} = {1}: {2}", cmplx1, cmplx2, cmplx1 == cmplx2);
Console.WriteLine("{0} = {1}: {2}", cmplx1, cmplx2, cmplx1.Equals(cmplx2));
}
}
// The example displays the following output:
//       (4, 1) <> (2, 1): True
//       (4, 1) = (2, 1): False
//       (4, 1) = (4, 1): True
//       (4, 1) = (4, 1): True
``````
``````Public Structure Complex
Public re, im As Double

Public Overrides Function Equals(ByVal obj As [Object]) As Boolean
Return TypeOf obj Is Complex AndAlso Me = CType(obj, Complex)
End Function

Public Overrides Function GetHashCode() As Integer
Return Tuple.Create(re, im).GetHashCode()
End Function

Public Shared Operator = (x As Complex, y As Complex) As Boolean
Return x.re = y.re AndAlso x.im = y.im
End Operator

Public Shared Operator <> (x As Complex, y As Complex) As Boolean
Return Not (x = y)
End Operator

Public Overrides Function ToString() As String
Return String.Format("({0}, {1})", re, im)
End Function
End Structure

Class Example
Public Shared Sub Main()
Dim cmplx1, cmplx2 As Complex

cmplx1.re = 4.0
cmplx1.im = 1.0

cmplx2.re = 2.0
cmplx2.im = 1.0

Console.WriteLine("{0} <> {1}: {2}", cmplx1, cmplx2, cmplx1 <> cmplx2)
Console.WriteLine("{0} = {1}: {2}", cmplx1, cmplx2, cmplx1.Equals(cmplx2))

cmplx2.re = 4.0

Console.WriteLine("{0} = {1}: {2}", cmplx1, cmplx2, cmplx1 = cmplx2)
Console.WriteLine("{0} = {1}: {2}", cmplx1, cmplx2, cmplx1.Equals(cmplx2))
End Sub
End Class
' The example displays the following output:
'       (4, 1) <> (2, 1): True
'       (4, 1) = (2, 1): False
'       (4, 1) = (4, 1): True
'       (4, 1) = (4, 1): True
``````

`Complex`値型であるから得ることはできません。Because `Complex` is a value type, it cannot be derived from. そのため、上書きをEquals(Object)メソッドを呼び出す必要はありませんGetTypeを確認する正確な実行時入力できますが、各オブジェクトの代わりに使用して、`is`演算子 (C#) または`TypeOf`の種類を確認するVisualbasicの演算子`obj`パラメーター。Therefore, the override to Equals(Object) method need not call GetType to determine the precise run-time type of each object, but can instead use the `is` operator in C# or the `TypeOf` operator in Visual Basic to check the type of the `obj` parameter.

### 注釈

• 現在のインスタンスが、参照型の場合、Equals(Object)参照の等価性のテストのメソッドと呼び出しをEquals(Object)メソッドへの呼び出しには、ReferenceEqualsメソッド。If the current instance is a reference type, the Equals(Object) method tests for reference equality, and a call to the Equals(Object) method is equivalent to a call to the ReferenceEquals method. 参照の等価性と比較されるオブジェクト変数が同じオブジェクトを参照していることを意味します。Reference equality means that the object variables that are compared refer to the same object. 次の例は、このような比較の結果を示しています。The following example illustrates the result of such a comparison. 定義、`Person`参照型である、クラスと呼び出し、`Person`新しい 2 つがインスタンス化するクラスのコンス トラクター`Person`オブジェクト、`person1a``person2`値が同じであります。It defines a `Person` class, which is a reference type, and calls the `Person` class constructor to instantiate two new `Person` objects, `person1a` and `person2`, which have the same value. 割り当てます`person1a`別のオブジェクト変数に`person1b`します。It also assigns `person1a` to another object variable, `person1b`. 例を示しますから出力として`person1a``person1b`が同じオブジェクトを参照するために等しい。As the output from the example shows, `person1a` and `person1b` are equal because they reference the same object. ただし、`person1a``person2`が、同じ値が等しいか、ありません。However, `person1a` and `person2` are not equal, although they have the same value.

``````using System;

// Define a reference type that does not override Equals.
public class Person
{
private string personName;

public Person(string name)
{
this.personName = name;
}

public override string ToString()
{
return this.personName;
}
}

public class Example
{
public static void Main()
{
Person person1a = new Person("John");
Person person1b = person1a;
Person person2 = new Person(person1a.ToString());

Console.WriteLine("Calling Equals:");
Console.WriteLine("person1a and person1b: {0}", person1a.Equals(person1b));
Console.WriteLine("person1a and person2: {0}", person1a.Equals(person2));

Console.WriteLine("\nCasting to an Object and calling Equals:");
Console.WriteLine("person1a and person1b: {0}", ((object) person1a).Equals((object) person1b));
Console.WriteLine("person1a and person2: {0}", ((object) person1a).Equals((object) person2));
}
}
// The example displays the following output:
//       person1a and person1b: True
//       person1a and person2: False
//
//       Casting to an Object and calling Equals:
//       person1a and person1b: True
//       person1a and person2: False
``````
``````' Define a reference type that does not override Equals.
Public Class Person
Private personName As String

Public Sub New(name As String)
Me.personName = name
End Sub

Public Overrides Function ToString() As String
Return Me.personName
End Function
End Class

Module Example
Public Sub Main()
Dim person1a As New Person("John")
Dim person1b As Person = person1a
Dim person2 As New Person(person1a.ToString())

Console.WriteLine("Calling Equals:")
Console.WriteLine("person1a and person1b: {0}", person1a.Equals(person1b))
Console.WriteLine("person1a and person2: {0}", person1a.Equals(person2))
Console.WriteLine()

Console.WriteLine("Casting to an Object and calling Equals:")
Console.WriteLine("person1a and person1b: {0}", CObj(person1a).Equals(CObj(person1b)))
Console.WriteLine("person1a and person2: {0}", CObj(person1a).Equals(CObj(person2)))
End Sub
End Module
' The example displays the following output:
'       Calling Equals:
'       person1a and person1b: True
'       person1a and person2: False
'
'       Casting to an Object and calling Equals:
'       person1a and person1b: True
'       person1a and person2: False
``````
• 現在のインスタンスが値の型の場合、Equals(Object)メソッドの値の等価性を調べます。If the current instance is a value type, the Equals(Object) method tests for value equality. 値の等価性には、次のことを意味します。Value equality means the following:

• 2 つのオブジェクトでは、同じ型です。The two objects are of the same type. 次の例に示すように、 Byte 12 の値を持つオブジェクトが等しくない、Int32を 2 つのオブジェクトがある実行時の型が異なるため、12 の値を持つオブジェクト。As the following example shows, a Byte object that has a value of 12 does not equal an Int32 object that has a value of 12, because the two objects have different run-time types.

``````using System;

public class Example
{
public static void Main()
{
byte value1 = 12;
int value2 = 12;

object object1 = value1;
object object2 = value2;

Console.WriteLine("{0} ({1}) = {2} ({3}): {4}",
object1, object1.GetType().Name,
object2, object2.GetType().Name,
object1.Equals(object2));
}
}
// The example displays the following output:
//        12 (Byte) = 12 (Int32): False
``````
``````Module Example
Public Sub Main()
Dim value1 As Byte = 12
Dim value2 As Integer = 12

Dim object1 As Object = value1
Dim object2 As Object = value2

Console.WriteLine("{0} ({1}) = {2} ({3}): {4}",
object1, object1.GetType().Name,
object2, object2.GetType().Name,
object1.Equals(object2))
End Sub
End Module
' The example displays the following output:
'       12 (Byte) = 12 (Int32): False
``````
• 2 つのオブジェクトのパブリックおよびプライベート フィールドの値が等しいです。The values of the public and private fields of the two objects are equal. 次の例は、値の等価性をテストします。The following example tests for value equality. 定義、`Person`構造体、値型であると呼び出し、`Person`新しい 2 つがインスタンス化するクラスのコンス トラクター`Person`オブジェクト、`person1``person2`値が同じであります。It defines a `Person` structure, which is a value type, and calls the `Person` class constructor to instantiate two new `Person` objects, `person1` and `person2`, which have the same value. 別のオブジェクトを参照してください、2 つのオブジェクト変数が、例の出力に示すよう`person1``person2`がプライベートの同じ値があるために等しい`personName`フィールド。As the output from the example shows, although the two object variables refer to different objects, `person1` and `person2` are equal because they have the same value for the private `personName` field.

``````using System;

// Define a value type that does not override Equals.
public struct Person
{
private string personName;

public Person(string name)
{
this.personName = name;
}

public override string ToString()
{
return this.personName;
}
}

public struct Example
{
public static void Main()
{
Person person1 = new Person("John");
Person person2 = new Person("John");

Console.WriteLine("Calling Equals:");
Console.WriteLine(person1.Equals(person2));

Console.WriteLine("\nCasting to an Object and calling Equals:");
Console.WriteLine(((object) person1).Equals((object) person2));
}
}
// The example displays the following output:
//       Calling Equals:
//       True
//
//       Casting to an Object and calling Equals:
//       True
``````
``````' Define a value type that does not override Equals.
Public Structure Person
Private personName As String

Public Sub New(name As String)
Me.personName = name
End Sub

Public Overrides Function ToString() As String
Return Me.personName
End Function
End Structure

Module Example
Public Sub Main()
Dim p1 As New Person("John")
Dim p2 As New Person("John")

Console.WriteLine("Calling Equals:")
Console.WriteLine(p1.Equals(p2))
Console.WriteLine()

Console.WriteLine("Casting to an Object and calling Equals:")
Console.WriteLine(CObj(p1).Equals(p2))
End Sub
End Module
' The example displays the following output:
'       Calling Equals:
'       True
'
'       Casting to an Object and calling Equals:
'       True
``````

Objectクラスは、.NET Framework のすべての型の基本クラス、Object.Equals(Object)メソッドは、他のすべての種類の既定の等値比較を提供します。Because the Object class is the base class for all types in the .NET Framework, the Object.Equals(Object) method provides the default equality comparison for all other types. 型が多くの場合、オーバーライド、ただし、Equals値の等価性を実装するメソッド。However, types often override the Equals method to implement value equality. 詳細については、ノートを呼び出し元とノート セクションでは継承クラスの参照します。For more information, see the Notes for Callers and Notes for Inheritors sections.

### ノートには、 Windows ランタイムWindows RuntimeNotes for the Windows ランタイムWindows Runtime

Windows ランタイムWindows Runtime c# または Visual Basic で記述されたクラスでオーバーライドできます、Equals(Object)メソッドのオーバー ロードします。classes that are written in C# or Visual Basic can override the Equals(Object) method overload.

### 呼び出し元のノートNotes for Callers

``````using System;
using System.Text;

public class Example
{
public static void Main()
{
StringBuilder sb1 = new StringBuilder("building a string...");
StringBuilder sb2 = new StringBuilder("building a string...");

Console.WriteLine("sb1.Equals(sb2): {0}", sb1.Equals(sb2));
Console.WriteLine("((Object) sb1).Equals(sb2): {0}",
((Object) sb1).Equals(sb2));
Console.WriteLine("Object.Equals(sb1, sb2): {0}",
Object.Equals(sb1, sb2));

Object sb3 = new StringBuilder("building a string...");
Console.WriteLine("\nsb3.Equals(sb2): {0}", sb3.Equals(sb2));
}
}
// The example displays the following output:
//       sb1.Equals(sb2): True
//       ((Object) sb1).Equals(sb2): False
//       Object.Equals(sb1, sb2): False
//
//       sb3.Equals(sb2): False
``````
``````Imports System.Text

Module Example
Public Sub Main()
Dim sb1 As New StringBuilder("building a string...")
Dim sb2 As New StringBuilder("building a string...")

Console.WriteLine("sb1.Equals(sb2): {0}", sb1.Equals(sb2))
Console.WriteLine("CObj(sb1).Equals(sb2): {0}",
CObj(sb1).Equals(sb2))
Console.WriteLine("Object.Equals(sb1, sb2): {0}",
Object.Equals(sb1, sb2))

Console.WriteLine()
Dim sb3 As Object = New StringBuilder("building a string...")
Console.WriteLine("sb3.Equals(sb2): {0}", sb3.Equals(sb2))
End Sub
End Module
' The example displays the following output:
'       sb1.Equals(sb2): True
'       CObj(sb1).Equals(sb2): False
'       Object.Equals(sb1, sb2): False
'
'       sb3.Equals(sb2): False
``````

### 継承時の注意Notes for Inheritors

その型が継承によって定義されている機能で、独自の型を定義するときに、`Equals`その基本型のメソッド。When you define your own type, that type inherits the functionality defined by the `Equals` method of its base type. 次の表の既定の実装、`Equals`の主要なカテゴリを .NET Framework 型のメソッド。The following table lists the default implementation of the `Equals` method for the major categories of types in the .NET Framework.

DelegateDelegate MulticastDelegate.Equals デリゲートには、同一の呼び出しリストと同じ型が必要です。Delegates must have the same type with identical invocation lists.
InterfaceInterface Object.Equals(Object) 参照の等価性。Reference equality.

オーバーライドする常に、値型のEqualsリフレクションに依存するテストが等しいかどうかは、パフォーマンスの低下を提供します。For a value type, you should always override Equals, because tests for equality that rely on reflection offer poor performance. 既定の実装をオーバーライドすることもできます。Equals参照型参照の等価性ではなく値の等価性をテストすると、値の等価性の正確な意味を定義します。You can also override the default implementation of Equals for reference types to test for value equality instead of reference equality and to define the precise meaning of value equality. このような実装のEquals返す`true`同じインスタンスでない場合でも、2 つのオブジェクトが同じの値があるかどうか。Such implementations of Equals return `true` if the two objects have the same value, even if they are not the same instance. 型の実行者は、オブジェクトの値を構成するものを決定する、通常は、一部またはすべてのデータ オブジェクトのインスタンス変数に格納されています。The type's implementer decides what constitutes an object's value, but it is typically some or all the data stored in the instance variables of the object. 値など、Stringオブジェクトは、文字列の文字に基づいて、String.Equals(Object)メソッドのオーバーライド、Object.Equals(Object)を返すメソッドを`true`いずれかの 2 つの文字列と同じ順序で同じ文字が含まれているインスタンス。For example, the value of a String object is based on the characters of the string; the String.Equals(Object) method overrides the Object.Equals(Object) method to return `true` for any two string instances that contain the same characters in the same order.

``````public class Person
{
private string idNumber;
private string personName;

public Person(string name, string id)
{
this.personName = name;
this.idNumber = id;
}

public override bool Equals(Object obj)
{
Person personObj = obj as Person;
if (personObj == null)
return false;
else
return idNumber.Equals(personObj.idNumber);
}

public override int GetHashCode()
{
return this.idNumber.GetHashCode();
}
}

public class Example
{
public static void Main()
{
Person p1 = new Person("John", "63412895");
Person p2 = new Person("Jack", "63412895");
Console.WriteLine(p1.Equals(p2));
Console.WriteLine(Object.Equals(p1, p2));
}
}
// The example displays the following output:
//       True
//       True
``````
``````Public Class Person
Private idNumber As String
Private personName As String

Public Sub New(name As String, id As String)
Me.personName = name
Me.idNumber = id
End Sub

Public Overrides Function Equals(obj As Object) As Boolean
Dim personObj As Person = TryCast(obj, Person)
If personObj Is Nothing Then
Return False
Else
Return idNumber.Equals(personObj.idNumber)
End If
End Function

Public Overrides Function GetHashCode() As Integer
Return Me.idNumber.GetHashCode()
End Function
End Class

Module Example
Public Sub Main()
Dim p1 As New Person("John", "63412895")
Dim p2 As New Person("Jack", "63412895")
Console.WriteLine(p1.Equals(p2))
Console.WriteLine(Object.Equals(p1, p2))
End Sub
End Module
' The example displays the following output:
'       True
'       True
``````

オーバーライドするだけでなくEquals、実装することができます、IEquatable<T>等しいかどうかを厳密に型指定されたテストを提供するインターフェイス。In addition to overriding Equals, you can implement the IEquatable<T> interface to provide a strongly typed test for equality.

• `x.Equals(x)` 返します`true`、浮動小数点型に関連する場合は除きます。`x.Equals(x)` returns `true`, except in cases that involve floating-point types.

• `x.Equals(y)` からは `y.Equals(x)` と同じ値が返されます。`x.Equals(y)` returns the same value as `y.Equals(x)`.

• `x.Equals(y)` 返します`true`両方`x``y``NaN`します。`x.Equals(y)` returns `true` if both `x` and `y` are `NaN`.

• 場合`(x.Equals(y) && y.Equals(z))`返します`true`、し`x.Equals(z)`返します`true`します。If `(x.Equals(y) && y.Equals(z))` returns `true`, then `x.Equals(z)` returns `true`.

• 連続して呼び出す`x.Equals(y)`によって参照されるオブジェクトと同じ値を返す`x``y`は変更されません。Successive calls to `x.Equals(y)` return the same value as long as the objects referenced by `x` and `y` are not modified.

• `x.Equals(null)` は、`false` を返します。`x.Equals(null)` returns `false`.

オーバーライドする場合は、次のガイドラインをに従ってEquals(Object):Follow these guidelines when overriding Equals(Object):

• 実装する型IComparableオーバーライドする必要がありますEquals(Object)します。Types that implement IComparable must override Equals(Object).

• オーバーライドする型Equals(Object)もオーバーライドする必要がありますGetHashCode。 そうしないと、ハッシュ テーブルが正しく機能しない可能性があります。Types that override Equals(Object) must also override GetHashCode; otherwise, hash tables might not work correctly.

• 実装を検討する必要があります、IEquatable<T>強くをサポートするインターフェイスが等しいかどうかのテストを入力します。You should consider implementing the IEquatable<T> interface to support strongly typed tests for equality. IEquatable<T>.Equals実装と一貫した結果を返す必要がありますEqualsします。Your IEquatable<T>.Equals implementation should return results that are consistent with Equals.

• 場合は、プログラミング言語が演算子のオーバー ロードをサポートしていると、指定された型に対して等値演算子をオーバー ロードする、オーバーライドすることも必要があります、Equals(Object)等値演算子と同じ結果を返します。If your programming language supports operator overloading and you overload the equality operator for a given type, you must also override the Equals(Object) method to return the same result as the equality operator. これにより、そのクラスのライブラリ コードを使用することを確認Equals(などArrayListHashtable) アプリケーション コードでは、等値演算子の使用方法と整合性があるように動作します。This helps ensure that class library code that uses Equals (such as ArrayList and Hashtable) behaves in a manner that is consistent with the way the equality operator is used by application code.

#### 参照型のガイドラインGuidelines for Reference Types

オーバーライドするに、次のガイドラインが適用Equals(Object)参照型。The following guidelines apply to overriding Equals(Object) for a reference type:

• オーバーライドを検討Equals場合、型のセマンティクスは、という事実に基づいての型がいくつかの値を表します。Consider overriding Equals if the semantics of the type are based on the fact that the type represents some value(s).

• ほとんどの参照型でする必要がありますをオーバーライドする場合でもを等値演算子をオーバー ロードしないEqualsします。Most reference types must not overload the equality operator, even if they override Equals. ただしなど、複雑な数値型の値のセマンティクスを持つが想定されている参照型を実装している場合は、等値演算子をオーバーライドする必要があります。However, if you are implementing a reference type that is intended to have value semantics, such as a complex number type, you must override the equality operator.

• オーバーライドしないでくださいEquals変更可能な参照型にします。You should not override Equals on a mutable reference type. これは、オーバーライドするためEqualsもオーバーライドする必要があります、GetHashCodeメソッド、前のセクションで説明したようにします。This is because overriding Equals requires that you also override the GetHashCode method, as discussed in the previous section. これは、ハッシュ テーブルで、オブジェクトが失われた可能性がありますが、有効期間中に変更可能な参照型のインスタンスのハッシュ コードを変更できることを意味します。This means that the hash code of an instance of a mutable reference type can change during its lifetime, which can cause the object to be lost in a hash table.

#### 値型のガイドラインGuidelines for Value Types

オーバーライドするに、次のガイドラインが適用Equals(Object)値型。The following guidelines apply to overriding Equals(Object) for a value type:

• 1 つまたは複数のフィールドを含む値型を定義する場合は参照型の値が、オーバーライドする必要がありますEquals(Object)します。If you are defining a value type that includes one or more fields whose values are reference types, you should override Equals(Object). Equals(Object)実装によって提供されるValueType値型がバイト単位の比較ではフィールドは、すべての値の型がリフレクションを使用して、フィールドが参照型を含む値型のフィールドの比較を実行します。The Equals(Object) implementation provided by ValueType performs a byte-by-byte comparison for value types whose fields are all value types, but it uses reflection to perform a field-by-field comparison of value types whose fields include reference types.

• 実装する必要があります、IEquatable<T>インターフェイス。You should implement the IEquatable<T> interface. 厳密に型指定された呼び出しIEquatable<T>.Equalsメソッドは、ボックス化を回避、`obj`引数。Calling the strongly typed IEquatable<T>.Equals method avoids boxing the `obj` argument.

こちらもご覧ください

## Equals(Object, Object)Equals(Object, Object)Equals(Object, Object)Equals(Object, Object)

``````public:
static bool Equals(System::Object ^ objA, System::Object ^ objB);``````
``public static bool Equals (object objA, object objB);``
``static member Equals : obj * obj -> bool``
``Public Shared Function Equals (objA As Object, objB As Object) As Boolean``

#### パラメーター

objA
Object Object Object Object

objB
Object Object Object Object

#### 戻り値

オブジェクトが等しいと見なされた場合は `true`。それ以外の場合は `false``true` if the objects are considered equal; otherwise, `false`. `objA``objB` の両方が null の場合、このメソッドは `true` を返します。If both `objA` and `objB` are null, the method returns `true`.

### 例

``````using System;

public class Example
{
public static void Main()
{
Dog m1 = new Dog("Alaskan Malamute");
Dog m2 = new Dog("Alaskan Malamute");
Dog g1 = new Dog("Great Pyrenees");
Dog g2 = g1;
Dog d1 = new Dog("Dalmation");
Dog n1 = null;
Dog n2 = null;

Console.WriteLine("null = null: {0}", Object.Equals(n1, n2));
Console.WriteLine("null Reference Equals null: {0}\n", Object.ReferenceEquals(n1, n2));

Console.WriteLine("{0} = {1}: {2}", g1, g2, Object.Equals(g1, g2));
Console.WriteLine("{0} Reference Equals {1}: {2}\n", g1, g2, Object.ReferenceEquals(g1, g2));

Console.WriteLine("{0} = {1}: {2}", m1, m2, Object.Equals(m1, m2));
Console.WriteLine("{0} Reference Equals {1}: {2}\n", m1, m2, Object.ReferenceEquals(m1, m2));

Console.WriteLine("{0} = {1}: {2}", m1, d1, Object.Equals(m1, d1));
Console.WriteLine("{0} Reference Equals {1}: {2}", m1, d1, Object.ReferenceEquals(m1, d1));
}
}

public class Dog
{
// Public field.
public string Breed;

// Class constructor.
public Dog(string dogBreed)
{
this.Breed = dogBreed;
}

public override bool Equals(Object obj)
{
if (obj == null || !(obj is Dog))
return false;
else
return this.Breed == ((Dog) obj).Breed;
}

public override int GetHashCode()
{
return this.Breed.GetHashCode();
}

public override string ToString()
{
return this.Breed;
}
}
// The example displays the following output:
//       null = null: True
//       null Reference Equals null: True
//
//       Great Pyrenees = Great Pyrenees: True
//       Great Pyrenees Reference Equals Great Pyrenees: True
//
//
//       Alaskan Malamute = Dalmation: False
//       Alaskan Malamute Reference Equals Dalmation: False
``````
``````Module Example
Public Sub Main()
Dim m1 As New Dog("Alaskan Malamute")
Dim m2 As New Dog("Alaskan Malamute")
Dim g1 As New Dog("Great Pyrenees")
Dim g2 As Dog = g1
Dim d1 As New Dog("Dalmation")
Dim n1 As Dog = Nothing
Dim n2 As Dog = Nothing

Console.WriteLine("null = null: {0}", Object.Equals(n1, n2))
Console.WriteLine("null Reference Equals null: {0}", Object.ReferenceEquals(n1, n2))
Console.WriteLine()

Console.WriteLine("{0} = {1}: {2}", g1, g2, Object.Equals(g1, g2))
Console.WriteLine("{0} Reference Equals {1}: {2}", g1, g2, Object.ReferenceEquals(g1, g2))
Console.WriteLine()

Console.WriteLine("{0} = {1}: {2}", m1, m2, Object.Equals(m1, m2))
Console.WriteLine("{0} Reference Equals {1}: {2}", m1, m2, Object.ReferenceEquals(m1, m2))
Console.WriteLine()

Console.WriteLine("{0} = {1}: {2}", m1, d1, Object.Equals(m1, d1))
Console.WriteLine("{0} Reference Equals {1}: {2}", m1, d1, Object.ReferenceEquals(m1, d1))
End Sub
End Module

Public Class Dog
' Public field.
Public Breed As String

' Class constructor.
Public Sub New(dogBreed As String)
Me.Breed = dogBreed
End Sub

Public Overrides Function Equals(obj As Object) As Boolean
If obj Is Nothing OrElse Not typeof obj Is Dog Then
Return False
Else
Return Me.Breed = CType(obj, Dog).Breed
End If
End Function

Public Overrides Function GetHashCode() As Integer
Return Me.Breed.GetHashCode()
End Function

Public Overrides Function ToString() As String
Return Me.Breed
End Function
End Class
' The example displays the following output:
'       null = null: True
'       null Reference Equals null: True
'
'       Great Pyrenees = Great Pyrenees: True
'       Great Pyrenees Reference Equals Great Pyrenees: True
'
'
'       Alaskan Malamute = Dalmation: False
'       Alaskan Malamute Reference Equals Dalmation: False
``````

### 注釈

• 2 つのオブジェクトが同じオブジェクト参照を表すかどうかを決定します。It determines whether the two objects represent the same object reference. かどうかは、これらは、メソッドを返します`true`します。If they do, the method returns `true`. このテストの呼び出しと同じですが、ReferenceEqualsメソッド。This test is equivalent to calling the ReferenceEquals method. さらに、両方`objA``objB`null、メソッドを返します`true`します。In addition, if both `objA` and `objB` are null, the method returns `true`.

• 判断したかどうか`objA`または`objB`nullIt determines whether either `objA` or `objB` is null. そのため、返された場合`false`します。If so, it returns `false`.

• 2 つのオブジェクトは、同じオブジェクト参照を表していないかどうか、およびはどちらもnull、呼び出す`objA`.`Equals`(`objB`) し、結果を返します。If the two objects do not represent the same object reference and neither is null, it calls `objA`.`Equals`(`objB`) and returns the result. つまり、`objA`オーバーライド、Object.Equals(Object)メソッドでは、このオーバーライドが呼び出されます。This means that if `objA` overrides the Object.Equals(Object) method, this override is called.

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