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IStructuralComparable.CompareTo Method

Tuple<T1, T2, T3, T4, T5, T6, T7, TRest>.IStructuralComparable.CompareTo Method

Compares the current Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> object to a specified object by using a specified comparer and returns an integer that indicates whether the current object is before, after, or in the same position as the specified object in the sort order.

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

int IStructuralComparable.CompareTo(
	Object other,
	IComparer comparer
)

Parameters

other
Type: System.Object
An object to compare with the current instance.
comparer
Type: System.Collections.IComparer
An object that provides custom rules for comparison.

Return Value

Type: System.Int32
A signed integer that indicates the relative position of this instance and other in the sort order, as shown in the following table.

Value

Description

A negative integer

This instance precedes other.

Zero

This instance and other have the same position in the sort order.

A positive integer

This instance follows other.

Implements

IStructuralComparable.CompareTo(Object, IComparer)

This member is an explicit interface implementation. It can be used only when the Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> instance is cast to an IStructuralComparable interface.

This method lets you define customized comparisons of Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> objects. For example, you can use this method to order Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> objects based on the value of a specific component.

Although this method can be called directly, it is most commonly called by collection-sorting methods that include IComparer parameters to order the members of a collection, such as the Array.Sort(Array, IComparer) method.

Caution noteCaution:

The IStructuralComparable.CompareTo method is intended for use in sorting operations. It should not be used when the primary purpose of a comparison is to determine whether two objects are equal. To determine whether two objects are equal, call the IStructuralEquatable.Equals method.

The following example creates an array of Tuple<T1, T2, T3, T4, T5, T6, T7, TRest> objects that contains population data for four U.S. cities from 1940 to 2000. The octuple's first component is the city name. The remaining six components represent the population at 10-year intervals from 1940 to 2000.

The PopulationComparer class provides an IComparer implementation that allows the array of octuples to be sorted by any one of its components. Two values are provided to the PopulationComparer class in its constructor: The position of the component that defines the sort order, and a Boolean value that indicates whether the tuple objects should be sorted in ascending or descending order.

The example then displays the elements in the array in unsorted order, sorts them by the third component (the population in 1950) and displays them, and then sorts them by the eighth component (the population in 2000) and displays them.


using System;
using System.Collections;
using System.Collections.Generic;

public class PopulationComparer<T1, T2, T3, T4, T5, T6, T7, T8> : IComparer
{
   private int itemPosition;
   private int multiplier = -1;

   public PopulationComparer(int component)
      : this(component, true)
   { }

   public PopulationComparer(int component, bool descending)
   {
      if (!descending) multiplier = 1;

      if (component <= 0 || component > 8)
         throw new ArgumentException("The component argument is out of range.");

      itemPosition = component;
   }

   public int Compare(object x, object y)
   {
      Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>> tX = x as Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>>;
      if (tX == null)
         return 0;

      Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>> tY = y as Tuple<T1, T2, T3, T4, T5, T6, T7, Tuple<T8>>;
      switch (itemPosition)
      {
         case 1:
            return Comparer<T1>.Default.Compare(tX.Item1, tY.Item1) * multiplier;
         case 2:
            return Comparer<T2>.Default.Compare(tX.Item2, tY.Item2) * multiplier;
         case 3:
            return Comparer<T3>.Default.Compare(tX.Item3, tY.Item3) * multiplier;
         case 4:
            return Comparer<T4>.Default.Compare(tX.Item4, tY.Item4) * multiplier;
         case 5:
            return Comparer<T5>.Default.Compare(tX.Item5, tY.Item5) * multiplier;
         case 6:
            return Comparer<T6>.Default.Compare(tX.Item6, tY.Item6) * multiplier;
         case 7:
            return Comparer<T7>.Default.Compare(tX.Item7, tY.Item7) * multiplier;
         case 8:
            return Comparer<T8>.Default.Compare(tX.Rest.Item1, tY.Rest.Item1) * multiplier;
         default:
            return Comparer<T1>.Default.Compare(tX.Item1, tY.Item1) * multiplier;
      }
   }
}

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create array of octuples with population data for three U.S. 
      // cities, 1940-2000.
      Tuple<string, int, int, int, int, int, int, Tuple<int>>[] cities = 
          { Tuple.Create("Los Angeles", 1504277, 1970358, 2479015, 2816061, 2966850, 3485398, 3694820),
            Tuple.Create("New York", 7454995, 7891957, 7781984, 7894862, 7071639, 7322564, 8008278),  
            Tuple.Create("Chicago", 3396808, 3620962, 3550904, 3366957, 3005072, 2783726, 2896016),  
            Tuple.Create("Detroit", 1623452, 1849568, 1670144, 1511462, 1203339, 1027974, 951270) };
      // Display array in unsorted order.
      outputBlock.Text += "In unsorted order:" + "\n";
      foreach (var city in cities)
         outputBlock.Text += city.ToString() + "\n";
      outputBlock.Text += "\n";

      Array.Sort(cities, new PopulationComparer<string, int, int, int, int, int, int, int>(2));

      // Display array in sorted order.
      outputBlock.Text += "Sorted by population in 1950:" + "\n";
      foreach (var city in cities)
         outputBlock.Text += city.ToString() + "\n";
      outputBlock.Text += "\n";

      Array.Sort(cities, new PopulationComparer<string, int, int, int, int, int, int, int>(8));

      // Display array in sorted order.
      outputBlock.Text += "Sorted by population in 2000:" + "\n";
      foreach (var city in cities)
         outputBlock.Text += city.ToString() + "\n";
   }
}
// The example displays the following output:
//    In unsorted order:
//    (Los Angeles, 1504277, 1970358, 2479015, 2816061, 2966850, 3485398, 3694820)
//    (New York, 7454995, 7891957, 7781984, 7894862, 7071639, 7322564, 8008278)
//    (Chicago, 3396808, 3620962, 3550904, 3366957, 3005072, 2783726, 2896016)
//    (Detroit, 1623452, 1849568, 1670144, 1511462, 1203339, 1027974, 951270)
//    
//    Sorted by population in 1950:
//    (New York, 7454995, 7891957, 7781984, 7894862, 7071639, 7322564, 8008278)
//    (Chicago, 3396808, 3620962, 3550904, 3366957, 3005072, 2783726, 2896016)
//    (Detroit, 1623452, 1849568, 1670144, 1511462, 1203339, 1027974, 951270)
//    (Los Angeles, 1504277, 1970358, 2479015, 2816061, 2966850, 3485398, 3694820)
//    
//    Sorted by population in 2000:
//    (New York, 7454995, 7891957, 7781984, 7894862, 7071639, 7322564, 8008278)
//    (Los Angeles, 1504277, 1970358, 2479015, 2816061, 2966850, 3485398, 3694820)
//    (Chicago, 3396808, 3620962, 3550904, 3366957, 3005072, 2783726, 2896016)
//    (Detroit, 1623452, 1849568, 1670144, 1511462, 1203339, 1027974, 951270)


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