Tuple<T1>.IStructuralEquatable.Equals(Object, IEqualityComparer) Method

Reference

Definition

Namespace:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: Tuple.cs

Source:: Tuple.cs

Source:: Tuple.cs

Important

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

 virtual bool System.Collections.IStructuralEquatable.Equals(System::Object ^ other, System::Collections::IEqualityComparer ^ comparer) = System::Collections::IStructuralEquatable::Equals;

bool IStructuralEquatable.Equals (object other, System.Collections.IEqualityComparer comparer);

abstract member System.Collections.IStructuralEquatable.Equals : obj * System.Collections.IEqualityComparer -> bool
override this.System.Collections.IStructuralEquatable.Equals : obj * System.Collections.IEqualityComparer -> bool

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

Parameters

other: Object

The object to compare with this instance.

comparer: IEqualityComparer

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

Returns

Boolean

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

Implements

Equals(Object, IEqualityComparer)

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).

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

   private static void TestEquality(Tuple<double> tuple, object obj)
   {
      Console.WriteLine("{0} = {1}: {2}", tuple.ToString(),
                                             obj.ToString(),
                                             ((IStructuralEquatable)tuple).Equals(obj, new Tuple1Comparer()));
   }
}
// The example displays the following output:
//       (12.3455) = (16.8912): False
//       (12.3455) = (12.3449599): True

open System
open System.Collections

type Tuple1Comparer() =
    interface IEqualityComparer with
        member _.Equals(x: obj, y: obj) =
            match x with
            | :? double as dblX -> 
                // Convert to Double values.
                let dblY = y :?> double
                if Double.IsNaN dblX || Double.IsInfinity dblX ||
                    Double.IsNaN dblY || Double.IsInfinity dblY then
                    dblX.Equals dblY
                else
                    abs (dblX - dblY) <= dblX * 0.0001
            | _ ->
                x.Equals y
                
        member _.GetHashCode(obj: obj) =
            obj.GetHashCode()

let testEquality (tuple: Tuple<double>) (obj: obj) =
    printfn $"{tuple} = {obj}: {(tuple :> IStructuralEquatable).Equals(obj, Tuple1Comparer())}"

let doubleTuple1 = Tuple.Create 12.3455
let doubleTuple2 = Tuple.Create 16.8912
let doubleTuple3 = Tuple.Create 12.3449599

// Compare first tuple with a Tuple<double> with a different value.
testEquality doubleTuple1 doubleTuple2
//Compare first tuple with a Tuple<double> with the same value.
testEquality doubleTuple1 doubleTuple3

// The example displays the following output:
//       (12.3455) = (16.8912): False
//       (12.3455) = (12.3449599): True

Imports System.Collections

Public Class Tuple1Comparer : Implements IEqualityComparer
   Public Overloads Function Equals(x As Object, 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 * .0001
         End If
      Else
         Return x.Equals(y)
      End If                    
   End Function
   
   Public Overloads Function GetHashCode(obj As Object) As Integer _
                   Implements IEqualityComparer.GetHashCode
      Return obj.GetHashCode()
   End Function
End Class

Module Example
   Public Sub Main()
      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(doubleTuple1, doubleTuple2)
      ' Compare first tuple with a Tuple(Of Double) with the same value.
      TestEquality(doubleTuple1, doubleTuple3)
   End Sub

   Private Sub TestEquality(tuple As Tuple(Of Double), obj As Object)
      Try
         Console.WriteLine("{0} = {1}: {2}", tuple.ToString(),
                                             obj.ToString,
                                             DirectCAst(tuple, IStructuralEquatable).Equals(obj, New Tuple1Comparer()))
      
      Catch e As ArgumentException
         If obj.GetType.IsGenericType Then 
            If obj.GetType().Name = "Tuple`1" Then 
               Console.WriteLine("Cannot compare a Tuple(Of {0}) with a Tuple(Of {1}).", 
                              tuple.Item1.GetType().Name, obj.Item1.GetType().Name)
            Else
               Console.WriteLine("Cannot compare a {0} with a {1}.", tuple.GetType().Name, 
                                                                     obj.GetType().Name)
            End If
         Else
            Console.WriteLine("Cannot compare a {0} with a {1}.", tuple.GetType().Name,
                                                                  obj.GetType().Name)
         End If
      End Try
   End Sub
End Module
' The example displays the following output:
'       (12.3455) = (16.8912): False
'       (12.3455) = (12.3449599): True

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 null, 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.

Applies to