IStructuralEquatable.Equals Method

Tuple(Of T1, T2, T3, T4, T5).IStructuralEquatable.Equals Method (Object, IEqualityComparer)


Returns a value that indicates whether the current Tuple(Of T1, T2, T3, T4, T5) object is equal to a specified object based on a specified comparison method.

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

Private Function Equals (
	other As Object,
	comparer As IEqualityComparer
) As Boolean
	Implements IStructuralEquatable.Equals


Type: System.Object

The object to compare with this instance.

Type: System.Collections.IEqualityComparer

An object that defines the method to use to evaluate whether the two objects are equal.

Return Value

Type: System.Boolean

true if the current instance is equal to the specified object; otherwise, false.

This member is an explicit interface member implementation. It can be used only when the Tuple(Of T1, T2, T3, T4, T5) instance is cast to an IStructuralEquatable interface.

The IEqualityComparer.Equals implementation is called only if other is not null, and if it can be successfully cast (in C#) or converted (in Visual Basic) to a Tuple(Of T1, T2, T3, T4, T5) object whose components are of the same types as the current instance. The IStructuralEquatable.Equals(Object, IEqualityComparer) method first passes the Item1 values of the Tuple(Of T1, T2, T3, T4, T5) objects to be compared to the IEqualityComparer.Equals implementation. If this method call returns true, the method is called again and passed the Item2 values of the two Tuple(Of T1, T2, T3, T4, T5) objects. This continues until the method call returns false when it compares a specific pair of Item values, or the two Item5 values are passed to the method.

The following example defines a DoubleComparer class that implements the IEqualityComparer interface. The example instantiates two Tuple(Of T1, T2, T3, T4, T5) objects by using a random number generator to populate their second through fifth components, casts the first instance to an IStructuralEquatable interface, and then uses a DoubleComparer object to test the two Tuple(Of T1, T2, T3, T4, T5) objects for approximate equality.

Imports System.Collections

Public Class DoubleComparer(Of T1, T2, T3, T4, T5) : Implements IEqualityComparer
   Private difference As Double
   Private argument As Integer = 0

   Public Sub New(difference As Double)
      Me.difference = difference
   End Sub

   Public Overloads Function Equals(x As Object, y As Object) As Boolean _
                   Implements IEqualityComparer.Equals
      argument += 1

      ' Return true for Item1.
      If argument = 1 Then
         Return True
         Dim d1 As Double = CDbl(x)
         Dim d2 As Double = CDbl(y)
         If d1 - d2 < d1 * difference Then
            Return True
            Return False
         End If
      End If
   End Function

   Public Overloads Function GetHashCode(obj As Object) As Integer _
                    Implements IEqualityComparer.GetHashCode
      If TypeOf obj Is T1 Then
         Return CType(obj, T1).GetHashCode()
      ElseIf TypeOf obj Is T2 Then
         Return CType(obj, T2).GetHashCode()
      ElseIf TypeOf obj Is T3 Then
         Return CType(Obj, T3).GetHashCode()
      ElseIf TypeOf obj Is T4 Then
         Return CType(Obj, T4).GetHashCode()
         Return CType(obj, T5).GetHashCode()
      End If
   End Function                
End Class

Module Example
   Public Sub Main()
      Dim value1 = GetValues(1)
      Dim value2 = GetValues(2)
      Dim iValue1 As IStructuralEquatable = value1
      Console.WriteLine("{0} ={3}{1} :{3}{2}", value1, value2, _
                        iValue1.Equals(value2, _
                        New DoubleComparer(Of Integer, Double, Double, Double, Double)(.01)), _
   End Sub

   Private Function GetValues(ctr As Integer) As Tuple(Of Integer, Double, Double, Double, Double)
      ' Generate four random numbers between 0 and 1
      Dim rnd As New Random(CInt((DateTime.Now.Ticks >> 32) >> ctr))
      Return Tuple.Create(ctr, rnd.NextDouble(), rnd.NextDouble(), 
                          rnd.NextDouble(), rnd.NextDouble)
   End Function                                   
End Module
' The example displays output like the following:
'    (1, 0.910850029862882, 0.894596965934428, 0.319678635019659, 0.801647342649124) =
'    (2, 0.818546649915421, 0.355961162762698, 0.0438506622071614, 0.679904267042831) :
'    False

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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