OrderedDictionary Class

1. 元素為DictionaryEnrty.
2. 不維持排序.
3. Key值不可為null.
4. Value可以為null.

Example

// The following code example enumerates the elements of a OrderedDictionary.
using System;
using System.Collections;
using System.Collections.Specialized;

public class OrderedDictionarySample
{
public static void Main()
{

// Creates and initializes a OrderedDictionary.
OrderedDictionary myOrderedDictionary = new OrderedDictionary();
myOrderedDictionary.Add("testKey1", "testValue1");
myOrderedDictionary.Add("testKey2", "testValue2");
myOrderedDictionary.Add("keyToDelete", "valueToDelete");
myOrderedDictionary.Add("testKey3", "testValue3");

ICollection keyCollection = myOrderedDictionary.Keys;
ICollection valueCollection = myOrderedDictionary.Values;

// Display the contents using the key and value collections
DisplayContents(keyCollection, valueCollection, myOrderedDictionary.Count);

// Modifying the OrderedDictionary
if (!myOrderedDictionary.IsReadOnly)
{
// Insert a new key to the beginning of the OrderedDictionary
myOrderedDictionary.Insert(0, "insertedKey1", "insertedValue1");

// Modify the value of the entry with the key "testKey2"
myOrderedDictionary["testKey2"] = "modifiedValue";

// Remove the last entry from the OrderedDictionary: "testKey3"
myOrderedDictionary.RemoveAt(myOrderedDictionary.Count - 1);

// Remove the "keyToDelete" entry, if it exists
if (myOrderedDictionary.Contains("keyToDelete"))
{
myOrderedDictionary.Remove("keyToDelete");
}
}

Console.WriteLine(
"{0}Displaying the entries of a modified OrderedDictionary.",
Environment.NewLine);
DisplayContents(keyCollection, valueCollection, myOrderedDictionary.Count);

// Clear the OrderedDictionary and add new values
myOrderedDictionary.Clear();
myOrderedDictionary.Add("newKey1", "newValue1");
myOrderedDictionary.Add("newKey2", "newValue2");
myOrderedDictionary.Add("newKey3", "newValue3");

// Display the contents of the "new" Dictionary using an enumerator
IDictionaryEnumerator myEnumerator =
myOrderedDictionary.GetEnumerator();

Console.WriteLine(
"{0}Displaying the entries of a \"new\" OrderedDictionary.",
Environment.NewLine);

DisplayEnumerator(myEnumerator);

Console.ReadLine();
}

// Displays the contents of the OrderedDictionary from its keys and values
public static void DisplayContents(
ICollection keyCollection, ICollection valueCollection, int dictionarySize)
{
String[] myKeys = new String[dictionarySize];
String[] myValues = new String[dictionarySize];
keyCollection.CopyTo(myKeys, 0);
valueCollection.CopyTo(myValues, 0);

// Displays the contents of the OrderedDictionary
Console.WriteLine(" INDEX KEY VALUE");
for (int i = 0; i < dictionarySize; i++)
{
Console.WriteLine(" {0,-5} {1,-25} {2}",
i, myKeys[i], myValues[i]);
}
Console.WriteLine();
}

// Displays the contents of the OrderedDictionary using its enumerator
public static void DisplayEnumerator(IDictionaryEnumerator myEnumerator)
{
Console.WriteLine(" KEY VALUE");
while (myEnumerator.MoveNext())
{
Console.WriteLine(" {0,-25} {1}",
myEnumerator.Key, myEnumerator.Value);
}
}
}

/*
This code produces the following output.

INDEX KEY VALUE
0 testKey1 testValue1
1 testKey2 testValue2
2 keyToDelete valueToDelete
3 testKey3 testValue3


Displaying the entries of a modified OrderedDictionary.
INDEX KEY VALUE
0 insertedKey1 insertedValue1
1 testKey1 testValue1
2 testKey2 modifiedValue


Displaying the entries of a "new" OrderedDictionary.
KEY VALUE
newKey1 newValue1
newKey2 newValue2
newKey3 newValue3

*/