Section 10.7. Sorting Arrays

10.7. Sorting Arrays

Two useful static methods from Table 10-1 that deserve a closer look are Sort ( ) and Reverse( ) . These methods do what you think they would: Reverse( ) reverses the order of elements in the array, and Sort( ) sorts the elements in order. These are fully supported for arrays of the built-in C# types, such as string , so sorting an array of strings puts the elements in alphabetical order, and sorting an array of ints puts them in numeric order. Making the Sort( ) method work with your own classes is a bit trickier, as you must implement the IComparable interface (see Chapter 13 for more on interfaces). Example 10-7 demonstrates the use of these two methods to manipulate String objects.

Example 10-7. Using Array.Sort and Array.Reverse

 using System; namespace ArraySortAndReverse {    public class Tester    {       public static void PrintMyArray( string[] theArray )       {          foreach ( string str in theArray )          {             Console.WriteLine( "Value: {0}", str );          }          Console.WriteLine( "\n" );       }       static void Main( )       {          String[] myArray =             {                 "Proust", "Faulkner", "Mann", "Hugo"             };          PrintMyArray( myArray );          Array.Reverse( myArray );          PrintMyArray( myArray );          String[] myOtherArray =             {                 "We", "Hold", "These", "Truths",                 "To", "Be", "Self","Evident",             };          PrintMyArray( myOtherArray );          Array.Sort( myOtherArray );          PrintMyArray( myOtherArray );       }    } } 

The output looks like this:

 Value: Proust     Value: Faulkner     Value: Mann     Value: Hugo     Value: Hugo     Value: Mann     Value: Faulkner     Value: Proust     Value: We     Value: Hold     Value: These     Value: Truths     Value: To     Value: Be     Value: Self     Value: Evident     Value: Be     Value: Evident     Value: Hold     Value: Self     Value: These     Value: To     Value: Truths     Value: We 

The example begins by creating myArray , an array of strings with the words:

 "Proust", "Faulkner", "Mann", "Hugo" 

This array is printed, and then passed to the Array.Reverse( ) method, where it is printed again to see that the array itself has been reversed :

 Value: Hugo     Value: Mann     Value: Faulkner     Value: Proust 

Similarly, the example creates a second array, myOtherArray , containing the words:

 "We", "Hold", "These", "Truths",     "To", "Be", "Self", "Evident", 

This is passed to the Array.Sort( ) method. Then Array.Sort( ) happily sorts them alphabetically :

 Value: Be     Value: Evident     Value: Hold     Value: Self     Value: These     Value: To     Value: Truths     Value: We 

Array.Sort( ) and Array.Reverse( ) are static methods, meaning you call them on the class, not the object, as discussed in Chapter 7. That means you don't call myArray.Reverse( ) to reverse the elements; instead, you call the static method and pass in the array as an argument, like this:

 Array.Reverse(myArray);