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Tuple<T1>.IStructuralEquatable.Equals Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Returns a value that indicates whether the current Tuple<T1> object is equal to a specified object based on a specified comparison method.

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

Syntax

'Declaration
Private Function Equals ( _
    other As Object, _
    comparer As IEqualityComparer _
) As Boolean Implements IStructuralEquatable.Equals
bool IStructuralEquatable.Equals(
    Object other,
    IEqualityComparer comparer
)

Parameters

  • other
    Type: System.Object
    The object to compare with this instance.

Return Value

Type: System.Boolean
true if the current instance is equal to the specified object; otherwise, false.

Implements

IStructuralEquatable.Equals(Object, IEqualityComparer)

Remarks

This member is an explicit interface member implementation. It can be used only when the Tuple<T1> instance is cast to an IStructuralEquatable interface.

The IEqualityComparer.Equals implementation is called only if other is not nulla null reference (Nothing in Visual Basic), and if it can be successfully cast (in C#) or converted (in Visual Basic) to a Tuple<T1> object whose single component is of the same type as the current instance. The method is passed the Item1 component of the current instance and the Item1 component of the Tuple<T1> object represented by the other parameter.

Examples

The following example defines an IEqualityComparer implementation that considers two floating-point values to be equal if they are approximately equal to each other (that is, if one value is within .01 percent of the other).

Imports System.Collections

Public Class Tuple1Comparer : Implements IEqualityComparer
   Public Overloads Function Equals(ByVal x As Object, ByVal y As Object) As Boolean _
                   Implements IEqualityComparer.Equals
      ' Check if x is a floating point type. If x is, then y is.
      If TypeOf x Is Double Or TypeOf x Is Single Then
         ' Convert to Double values.
         Dim dblX As Double = CDbl(x)
         Dim dblY As Double = CDbl(y)
         If Double.IsNaN(dblX) Or Double.IsInfinity(dblX) Or _
            Double.IsNaN(dblY) Or Double.IsInfinity(dblY) Then
            Return dblX.Equals(dblY)
         Else
            Return Math.Abs(dblX - dblY) <= dblY * 0.0001
         End If
      Else
         Return x.Equals(y)
      End If
   End Function

   Public Overloads Function GetHashCode(ByVal obj As Object) As Integer _
                   Implements IEqualityComparer.GetHashCode
      Return obj.GetHashCode()
   End Function
End Class

Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim doubleTuple1 = Tuple.Create(12.3455)

      Dim doubleTuple2 = Tuple.Create(16.8912)
      Dim doubleTuple3 = Tuple.Create(12.3449599)

      ' Compare first tuple with a Tuple(Of Double) with a different value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple2)
      ' Compare first tuple with a Tuple(Of Double) with the same value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple3)
   End Sub

   Private Sub TestEquality(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal tuple As Tuple(Of Double), ByVal obj As Object)
      Try
         outputBlock.Text += String.Format("{0} = {1}: {2}", tuple.ToString(), _
                                             obj.ToString, _
                                             DirectCast(tuple, IStructuralEquatable).Equals(obj, New Tuple1Comparer())) & vbCrLf

      Catch e As ArgumentException
         If obj.GetType.IsGenericType Then
            If obj.GetType().Name = "Tuple`1" Then
               outputBlock.Text += String.Format("Cannot compare a Tuple(Of {0}) with a Tuple(Of {1}).", _ 
                              tuple.Item1.GetType().Name, obj.Item1.GetType().Name) & vbCrLf
            Else
               outputBlock.Text += String.Format("Cannot compare a {0} with a {1}.", tuple.GetType().Name, _ 
                                                                     obj.GetType().Name) & vbCrLf
            End If
         Else
            outputBlock.Text += String.Format("Cannot compare a {0} with a {1}.", tuple.GetType().Name, _
                                                                  obj.GetType().Name) & vbCrLf
         End If
      End Try
   End Sub
End Module
' The example displays the following output:
'       (12.3455) = (16.8912): False
'       (12.3455) = (12.3449599): True
using System;
using System.Collections;

public class Tuple1Comparer : IEqualityComparer
{
   new public bool Equals(object x, object y)
   {
      // Check if x is a floating point type. If x is, then y is.
      if (x is double | x is float)
      {
         // Convert to Double values.
         double dblX = (double)x;
         double dblY = (double)y;
         if (Double.IsNaN(dblX) | Double.IsInfinity(dblX) |
             Double.IsNaN(dblY) | Double.IsInfinity(dblY))
            return dblX.Equals(dblY);
         else
            return Math.Abs(dblX - dblY) <= dblX * .0001;
      }
      else
      {
         return x.Equals(y);
      }
   }

   public int GetHashCode(object obj)
   {
      return obj.GetHashCode();
   }
}

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      var doubleTuple1 = Tuple.Create(12.3455);

      var doubleTuple2 = Tuple.Create(16.8912);
      var doubleTuple3 = Tuple.Create(12.3449599);

      // Compare first tuple with a Tuple<double> with a different value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple2);
      //Compare first tuple with a Tuple<double> with the same value.
      TestEquality(outputBlock, doubleTuple1, doubleTuple3);
   }

   private static void TestEquality(System.Windows.Controls.TextBlock outputBlock, Tuple<double> tuple, object obj)
   {
      outputBlock.Text += String.Format("{0} = {1}: {2}", tuple.ToString(),
                                             obj.ToString(),
                                             ((IStructuralEquatable)tuple).Equals(obj, new Tuple1Comparer())) + "\n";
   }
}
// The example displays the following output:
//       (12.3455) = (16.8912): False
//       (12.3455) = (12.3449599): True

Version Information

Silverlight

Supported in: 5, 4

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.