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Inglés

Double.Equals (Método) (Object)

 

Devuelve un valor que indica si esta instancia equivale a un objeto especificado.

Espacio de nombres:   System
Ensamblado:  mscorlib (en mscorlib.dll)

public override bool Equals(
	object obj
)

Parámetros

obj

Objeto que se va a comparar con esta instancia.

Valor devuelto

Type: System.Boolean

Es true si obj es una instancia de Double y es igual al valor de esta instancia; en caso contrario, es false.

The Equals method should be used with caution, because two apparently equivalent values can be unequal due to the differing precision of the two values.The following example reports that the Double value .3333 and the Double returned by dividing 1 by 3 are unequal.

// Initialize two doubles with apparently identical values
double double1 = .33333;
object double2 = 1/3;
// Compare them for equality
Console.WriteLine(double1.Equals(double2));    // displays false

For alternatives to calling the Equals method, see the documentation for the Equals(Double) overload.

System_CAPS_noteNota

Because Epsilon defines the minimum expression of a positive value whose range is near zero, the margin of difference between two similar values must be greater than Epsilon.Typically, it is many times greater than Epsilon.

The precision of floating-point numbers beyond the documented precision is specific to the implementation and version of the .NET Framework.Consequently, a comparison of two particular numbers might change between versions of the .NET Framework because the precision of the numbers' internal representation might change.

If two Double.NaN values are tested for equality by calling the Equals method, the method returns true.However, if two NaN values are tested for equality by using the equality operator, the operator returns false.When you want to determine whether the value of a Double is not a number (NaN), an alternative is to call the IsNaN method.

Notas para los llamadores:

Compiler overload resolution may account for an apparent difference in the behavior of the two Equals method overloads.If an implicit conversion between the obj argument and a Double is defined and the argument is not typed as an Object, compilers may perform an implicit conversion and call the Equals(Double) method.Otherwise, they call the Equals(Object) method, which always returns false if its obj argument is not a Double value.The following example illustrates the difference in behavior between the two method overloads.In the case of all primitive numeric types except for Decimal and in C#, the first comparison returns true because the compiler automatically performs a widening conversion and calls the Equals(Double) method, whereas the second comparison returns false because the compiler calls the Equals(Object) method.

using System;

public class Example
{
   static double value = 112;

   public static void Main()
   {
      byte byte1= 112;
      Console.WriteLine("value = byte1: {0,16}", value.Equals(byte1));
      TestObjectForEquality(byte1);

      short short1 = 112;
      Console.WriteLine("value = short1: {0,16}", value.Equals(short1));
      TestObjectForEquality(short1);

      int int1 = 112;
      Console.WriteLine("value = int1: {0,18}", value.Equals(int1));
      TestObjectForEquality(int1);

      long long1 = 112;
      Console.WriteLine("value = long1: {0,17}", value.Equals(long1));
      TestObjectForEquality(long1);

      sbyte sbyte1 = 112;
      Console.WriteLine("value = sbyte1: {0,16}", value.Equals(sbyte1));
      TestObjectForEquality(sbyte1);

      ushort ushort1 = 112;
      Console.WriteLine("value = ushort1: {0,16}", value.Equals(ushort1));
      TestObjectForEquality(ushort1);

      uint uint1 = 112;
      Console.WriteLine("value = uint1: {0,18}", value.Equals(uint1));
      TestObjectForEquality(uint1);

      ulong ulong1 = 112;
      Console.WriteLine("value = ulong1: {0,17}", value.Equals(ulong1));
      TestObjectForEquality(ulong1);

      decimal dec1 = 112m;
      Console.WriteLine("value = dec1: {0,21}", value.Equals(dec1));
      TestObjectForEquality(dec1);

      float sng1 = 112;
      Console.WriteLine("value = sng1: {0,19}", value.Equals(sng1));
      TestObjectForEquality(sng1);
   }

   private static void TestObjectForEquality(Object obj)
   {
      Console.WriteLine("{0} ({1}) = {2} ({3}): {4}\n",
                        value, value.GetType().Name,
                        obj, obj.GetType().Name,
                        value.Equals(obj));
   }
}
// The example displays the following output:
//       value = byte1:             True
//       112 (Double) = 112 (Byte): False
//
//       value = short1:             True
//       112 (Double) = 112 (Int16): False
//
//       value = int1:               True
//       112 (Double) = 112 (Int32): False
//
//       value = long1:              True
//       112 (Double) = 112 (Int64): False
//
//       value = sbyte1:             True
//       112 (Double) = 112 (SByte): False
//
//       value = ushort1:             True
//       112 (Double) = 112 (UInt16): False
//
//       value = uint1:               True
//       112 (Double) = 112 (UInt32): False
//
//       value = ulong1:              True
//       112 (Double) = 112 (UInt64): False
//
//       value = dec1:                 False
//       112 (Double) = 112 (Decimal): False
//
//       value = sng1:                True
//       112 (Double) = 112 (Single): False

Universal Windows Platform
Disponible desde 4.5
.NET Framework
Disponible desde 1.1
Portable Class Library
Compatible con: portable .NET platforms
Silverlight
Disponible desde 2.0
Windows Phone Silverlight
Disponible desde 7.0
Windows Phone
Disponible desde 8.1
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