C# 0 The Complete Reference

PART II

C h a p t e r   2 4 :  

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When enumerated, 

SortedDictionary

 returns key/value pairs in the form of a 

KeyValuePair

 structure. Recall that this structure defines the following two fields:

public TK Key;

public TV Value;

These fields hold the key or value associated with an entry. Most of the time you won’t need 

to use 

KeyValuePair

 directly because 

SortedDictionary

 allows you to 

work the keys and values individually. However, when enumerating a 

SortedDictionary

, such as in a 

foreach

 loop, the objects being enumerated are 

KeyValuePair

s.

In a 

SortedDictionary

, all keys must be unique, and a key must not change 

while it is in use as a key. Values need not be unique.

Here is an example that demonstrates 

SortedDictionary

. It reworks the 

Dictionary

 example shown in the preceding section. In this version, the database 

of employees and salaries is sorted based on name (which is the key).

// Demonstrate the generic SortedDictionary class.

using System;

using System.Collections.Generic;

class GenSortedDictionaryDemo {

  static void Main() {

    // Create a Dictionary that holds employee

    // names and their corresponding salary.

    SortedDictionary dict =

      new SortedDictionary();

    // Add elements to the collection.

    dict.Add("Butler, John", 73000);

    dict.Add("Swartz, Sarah", 59000);

    dict.Add("Pyke, Thomas", 45000);

    dict.Add("Frank, Ed", 99000);

    // Get a collection of the keys (names).

    ICollection c = dict.Keys;

    // Use the keys to obtain the values (salaries).

    foreach(string str in c)

      Console.WriteLine("{0}, Salary: {1:C}", str, dict[str]);

  }

}

The output is shown here:

Butler, John, Salary: $73,000.00

Frank, Ed, Salary: $99,000.00

Pyke, Thomas, Salary: $45,000.00

Swartz, Sarah, Salary: $59,000.00

As you can see, the list is now sorted based on the key, which is the employee’s name.

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