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Classe Object

 

Publicado: agosto de 2016

Suporta todas as classes na hierarquia de classes do .NET Framework e fornece serviços de baixo nível para classes derivadas. Esta é a classe base definitiva de todas as classes do .NET Framework. É a raiz da hierarquia de tipo.

Para procurar esse tipo no código-fonte do .NET Framework, consulte a Reference Source (Fonte de referência).

Namespace:   System
Assembly:  mscorlib (em mscorlib.dll)

System.Object
   Todas as classes, estruturas, enumerações e delegados.

[SerializableAttribute]
[ClassInterfaceAttribute(ClassInterfaceType.AutoDual)]
[ComVisibleAttribute(true)]
public class Object

NomeDescrição
System_CAPS_pubmethodObject()

Inicializa uma nova instância da classe Object.

NomeDescrição
System_CAPS_pubmethodEquals(Object)

Verifica se o objeto especificado é igual ao objeto atual.

System_CAPS_pubmethodSystem_CAPS_staticEquals(Object, Object)

Determina se as instâncias dos objetos especificados são consideradas iguais.

System_CAPS_protmethodFinalize()

Permite que um objeto tente liberar recursos e executar outras operações de limpeza antes que ele seja recuperado pela coleta de lixo.

System_CAPS_pubmethodGetHashCode()

Serve como a função de hash padrão.

System_CAPS_pubmethodGetType()

Obtém o Type da instância atual.

System_CAPS_protmethodMemberwiseClone()

Cria uma cópia superficial do Object atual.

System_CAPS_pubmethodSystem_CAPS_staticReferenceEquals(Object, Object)

Determina se as instâncias de Object especificadas são a mesma instância.

System_CAPS_pubmethodToString()

Retorna uma string que representa o objeto atual.

System_CAPS_noteObservação

To view the .NET Framework source code for this type, see the Reference Sourcehttp://referencesource.microsoft.com/#mscorlib/system/object.cs#d9262ceecc1719ab. 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 instructionshttp://referencesource.microsoft.com/.

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

Because all classes in the .NET Framework are derived from T:System.Object, every method defined in the T:System.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.

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 T:System.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 T:System.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 T:System.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 T:System.Object class and overrides many of the virtual methods of the T:System.Object class. In addition, the example shows how to call many of the static and instance methods of the T:System.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.
        Point 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 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();
    }
}

public sealed class App {
    static void Main() 
    {
        // Construct a Point object.
        Point p1 = new 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 example produces the following output:
//
// False
// True
// True
// p1's value is: (1, 2)
//

Plataforma Universal do Windows
Disponível desde 8
.NET Framework
Disponível desde 1.1
Biblioteca de Classes Portátil
Com suporte no: plataformas portáteis do .NET
Silverlight
Disponível desde 2.0
Windows Phone Silverlight
Disponível desde 7.0
Windows Phone
Disponível desde 8.1

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

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