Tuple<T1,T2,T3,T4>.IStructuralEquatable.Equals Method

Definition

Namespace:

System

Assemblies:

netstandard.dll, System.Runtime.dll

Source:

Tuple.cs

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

C#

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

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 Item3And4Comparer class that implements the IEqualityComparer interface and changes the way in which Tuple<T1,T2,T3,T4> objects are evaluated for equality. The method always returns true when it is passed the Item1 and Item2 property values of two Tuple<T1,T2,T3,T4> objects, and it calls the obj.Equals method to evaluate their Item3 property values. It this method call returns true, it also calls the obj.Equals method to evaluate the tuples' Item4 property values. As a result, the method tests for equality based only on the values of the Item3 and Item4 properties. The output illustrates the result for a data set of Tuple<T1,T2,T3,T4> objects that record the name of a U.S. city, the month of a year, and the average high and low temperature for that month.

C#

using System;
using System.Collections;

public class Item3And4Comparer<T1, T2, T3, T4> : IEqualityComparer
{
   private int argument = 0;
   
   new public bool Equals(object x, object y)
   {
      argument++;
      
      // Return true for all values of Item1, Item2.
      if (argument <= 2)
         return true;
      else
         return x.Equals(y);
   }
   
   public int GetHashCode(object obj)
   {
      if (obj is T1)
         return ((T1) obj).GetHashCode();
      else if (obj is T2)
         return ((T2) obj).GetHashCode();
      else if (obj is T3)
         return ((T3) obj).GetHashCode();
      else
         return ((T4) obj).GetHashCode();
   }
}

public class Example
{
   public static void Main()
   {
      Tuple<string, int, double, double>[] temperatures = 
            { Tuple.Create("New York, NY", 4, 61.0, 43.0),
              Tuple.Create("Chicago, IL", 2, 34.0, 18.0), 
              Tuple.Create("Newark, NJ", 4, 61.0, 43.0),
              Tuple.Create("Boston, MA", 6, 77.0, 59.0),
              Tuple.Create("Detroit, MI", 9, 74.0, 53.0),
              Tuple.Create("Minneapolis, MN", 8, 81.0, 61.0) }; 
      // Compare each item with every other item for equality.
      for (int ctr = 0; ctr < temperatures.Length; ctr++)
      {
         IStructuralEquatable temperatureInfo = temperatures[ctr];
         for (int ctr2 = ctr + 1; ctr2 < temperatures.Length; ctr2++)
            Console.WriteLine("{0} = {1}: {2}", 
                              temperatureInfo, temperatures[ctr2], 
                              temperatureInfo.Equals(temperatures[ctr2], 
                                              new Item3And4Comparer<string, int, double, double>()));

         Console.WriteLine();                                               
      }
   }
}
// The example displays the following output:
//    (New York, NY, 4, 61, 43) = (Chicago, IL, 2, 34, 18): False
//    (New York, NY, 4, 61, 43) = (Newark, NJ, 4, 61, 43): True
//    (New York, NY, 4, 61, 43) = (Boston, MA, 6, 77, 59): False
//    (New York, NY, 4, 61, 43) = (Detroit, MI, 9, 74, 53): False
//    (New York, NY, 4, 61, 43) = (Minneapolis, MN, 8, 81, 61): False
//    
//    (Chicago, IL, 2, 34, 18) = (Newark, NJ, 4, 61, 43): False
//    (Chicago, IL, 2, 34, 18) = (Boston, MA, 6, 77, 59): False
//    (Chicago, IL, 2, 34, 18) = (Detroit, MI, 9, 74, 53): False
//    (Chicago, IL, 2, 34, 18) = (Minneapolis, MN, 8, 81, 61): False
//    
//    (Newark, NJ, 4, 61, 43) = (Boston, MA, 6, 77, 59): False
//    (Newark, NJ, 4, 61, 43) = (Detroit, MI, 9, 74, 53): False
//    (Newark, NJ, 4, 61, 43) = (Minneapolis, MN, 8, 81, 61): False
//    
//    (Boston, MA, 6, 77, 59) = (Detroit, MI, 9, 74, 53): False
//    (Boston, MA, 6, 77, 59) = (Minneapolis, MN, 8, 81, 61): False
//    
//    (Detroit, MI, 9, 74, 53) = (Minneapolis, MN, 8, 81, 61): False

Remarks

This member is an explicit interface member implementation. It can be used only when the Tuple<T1,T2,T3,T4> 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,T2,T3,T4> 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<T1,T2,T3,T4> 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,T3,T4> objects. If this method call returns true again, the method is called a third time and passed the Item3 values of the two Tuple<T1,T2,T3,T4> objects. If this method call returns true again, the method is called for the fourth and final time and passed the Item4 values of the two Tuple<T1,T2,T3,T4> objects.

Applies to