IComparable Interface

Defines a generalized type-specific comparison method that a value type or class implements to order or sort its instances.

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

public interface IComparable

The IComparable type exposes the following members.

Public methodSupported by Silverlight for Windows PhoneSupported by Xbox 360CompareToCompares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.

This interface is implemented by types whose values can be ordered or sorted. It requires that implementing types define a single method, CompareTo, that indicates whether the position of the current instance in the sort order is before, after, or the same as a second object of the same type. The instance's IComparable implementation is called automatically by methods such as Array.Sort.

All numeric types (such as Int32 and Double) implement IComparable, as do String, Char, and DateTime. Custom types should also provide their own implementation of IComparable to allow object instances to be ordered or sorted.

The following code sample illustrates the implementation of IComparable and the requisite CompareTo method.

using System;
using System.Collections;

public class Temperature : IComparable
   // The temperature value
   protected double temperatureF;

   public int CompareTo(object obj)
      if (obj == null) return 1;

      Temperature otherTemperature = obj as Temperature;
      if (otherTemperature != null)
         return this.temperatureF.CompareTo(otherTemperature.temperatureF);
         throw new ArgumentException("Object is not a Temperature");

   public double Fahrenheit
         return this.temperatureF;
         this.temperatureF = value;

   public double Celsius
         return (this.temperatureF - 32) * (5.0 / 9);
         this.temperatureF = (value * 9.0 / 5) + 32;

public class Example
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
      Temperature[] temperatures = new Temperature[10];
      // Initialize random number generator.
      Random rnd = new Random();

      // Generate 10 temperatures between 0 and 100 randomly.
      for (int ctr = 1; ctr <= 10; ctr++)
         int degrees = rnd.Next(0, 100);
         Temperature temp = new Temperature();
         temp.Fahrenheit = degrees;
         temperatures[ctr - 1] = temp;

      // Sort ArrayList.

      foreach (Temperature temp in temperatures)
         outputBlock.Text += temp.Fahrenheit + "\n";

// The example displays the following output (individual
// values may vary because they are randomly generated):
//       2
//       7
//       16
//       17
//       31
//       37
//       58
//       66
//       72
//       95


Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

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

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