Tuple<T1,T2>.IStructuralEquatable.Equals 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

Returns

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

Implements

Examples

The following example defines an Item2Comparer class that implements the IEqualityComparer interface and changes the way in which Tuple<T1,T2> objects are evaluated for equality. The method always returns true when it is passed the Item1 property values of two Tuple<T1,T2> objects, and it calls the IStructuralEquatable.Equals method to evaluate their Item2 property values. As a result, the method tests for equality based only on the value of the Item2 property. The output illustrates the result for a data set of Tuple<T1,T2> objects that record the names of runners and the distances that they ran.

using System;
using System.Collections;

public class Item2Comparer<T1, T2> : IEqualityComparer
{
   new public bool Equals(object x, object y)
   {
      // Return true for all values of Item1.
      if (x is T1)
      //if (typeof(x) is string) 
         return true;
      else
         return x.Equals(y);
   }
   
   public int GetHashCode(object obj)
   {
      if (obj is T1)
         return ((T1) obj).GetHashCode();
      else
         return ((T2) obj).GetHashCode();
   }                
}

public class Example
{
   public static void Main()
   {
      Tuple<string, double>[] distancesWalked = {
                        Tuple.Create("Jan", Double.NaN), 
                        Tuple.Create("Joe", Double.NaN), 
                        Tuple.Create("Adam", 1.36), 
                        Tuple.Create("Selena", 2.01),
                        Tuple.Create("Jake", 1.36) };
      for (int ctr = 0; ctr < distancesWalked.Length; ctr++)
      {
         Tuple<string, double> distanceWalked = distancesWalked[ctr];
         for (int ctr2 = ctr + 1; ctr2 < distancesWalked.Length; ctr2++)
         {
            Console.WriteLine("{0} = {1}: {2}", distanceWalked, 
                              distancesWalked[ctr2], 
                              ((IStructuralEquatable)distanceWalked).Equals(distancesWalked[ctr2], 
                                                    new Item2Comparer<string, double>()));
         }
         Console.WriteLine();
      }   
   }
}
// The example displays the following output:
//       (Jan, NaN) = (Joe, NaN): True
//       (Jan, NaN) = (Adam, 1.36): False
//       (Jan, NaN) = (Selena, 2.01): False
//       (Jan, NaN) = (Jake, 1.36): False
//       
//       (Joe, NaN) = (Adam, 1.36): False
//       (Joe, NaN) = (Selena, 2.01): False
//       (Joe, NaN) = (Jake, 1.36): False
//       
//       (Adam, 1.36) = (Selena, 2.01): False
//       (Adam, 1.36) = (Jake, 1.36): True
//       
//       (Selena, 2.01) = (Jake, 1.36): False

open System
open System.Collections

type Item2Comparer<'T1, 'T2 when 'T1: equality and 'T2: equality>() = 
    interface IEqualityComparer with    
        member _.GetHashCode(obj) =
            match obj with
            | :? 'T1 as obj->
                obj.GetHashCode()
            | _ ->
                (obj :?> 'T2).GetHashCode()

        member _.Equals(x, y) =
            // Return true for all values of Item1.
            match x with
            | :? 'T1 ->
                true
            | _ ->
                x.Equals y

let distancesWalked =
    [| Tuple.Create("Jan", Double.NaN) 
       Tuple.Create("Joe", Double.NaN) 
       Tuple.Create("Adam", 1.36)
       Tuple.Create("Selena", 2.01)
       Tuple.Create("Jake", 1.36) |]

for ctr = 0 to distancesWalked.Length - 1 do
    let distanceWalked = distancesWalked[ctr]
    for ctr2 = ctr + 1 to distancesWalked.Length - 1 do
        printfn $"{distanceWalked} = {distancesWalked[ctr2]}: {(distanceWalked :> IStructuralEquatable).Equals(distancesWalked[ctr2], Item2Comparer<string, double>())}"
    printfn ""
// The example displays the following output:
//       (Jan, NaN) = (Joe, NaN): True
//       (Jan, NaN) = (Adam, 1.36): False
//       (Jan, NaN) = (Selena, 2.01): False
//       (Jan, NaN) = (Jake, 1.36): False
//       
//       (Joe, NaN) = (Adam, 1.36): False
//       (Joe, NaN) = (Selena, 2.01): False
//       (Joe, NaN) = (Jake, 1.36): False
//       
//       (Adam, 1.36) = (Selena, 2.01): False
//       (Adam, 1.36) = (Jake, 1.36): True
//       
//       (Selena, 2.01) = (Jake, 1.36): False

Imports System.Collections

Public Class Item2Comparer(Of T1, T2) : Implements IEqualityComparer
   
   Public Overloads Function Equals(x As Object, y As Object) As Boolean _
                   Implements IEqualityComparer.Equals
      ' Return true for all values of Item1.
      If TypeOf x Is T1 Then
         Return True
      Else
         Return x.Equals(y)
      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()
      Else
         Return CType(obj, T2).GetHashCode()
      End If   
   End Function                
End Class

Module Example
   Public Sub Main()
      Dim distancesWalked() = {
                        Tuple.Create("Jan", Double.NaN), 
                        Tuple.Create("Joe", Double.NaN), 
                        Tuple.Create("Adam", 1.36), 
                        Tuple.Create("Selena", 2.01),
                        Tuple.Create("Jake", 1.36) }
      For ctr As Integer = 0 To distancesWalked.Length - 1
         Dim distanceWalked As Tuple(Of String, Double) = distancesWalked(ctr)
         For ctr2 As Integer = ctr + 1 To distancesWalked.Length - 1
            Console.WriteLine("{0} = {1}: {2}", distanceWalked, 
                              distancesWalked(ctr2), 
                              DirectCast(distanceWalked, IStructuralEquatable).Equals(distancesWalked(ctr2), 
                                                    new Item2Comparer(Of String, Double)))
         Next
         Console.WriteLine()
      Next                     
   End Sub
End Module
' The example displays the following output:
'       (Jan, NaN) = (Joe, NaN): True
'       (Jan, NaN) = (Adam, 1.36): False
'       (Jan, NaN) = (Selena, 2.01): False
'       (Jan, NaN) = (Jake, 1.36): False
'       
'       (Joe, NaN) = (Adam, 1.36): False
'       (Joe, NaN) = (Selena, 2.01): False
'       (Joe, NaN) = (Jake, 1.36): False
'       
'       (Adam, 1.36) = (Selena, 2.01): False
'       (Adam, 1.36) = (Jake, 1.36): True
'       
'       (Selena, 2.01) = (Jake, 1.36): False

Remarks

This member is an explicit interface member implementation. It can be used only when the Tuple<T1,T2> instance is cast to an IStructuralEquatable interface.

The IStructuralEquatable.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,T2> object whose components are of the same types as the current instance. The IStructuralEquatable.Equals method first passes the Item1 values of the Tuple<T1,T2> 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<T1,T2> objects.

Applies to

See also

• IEqualityComparer