OrderedDictionary Class (System.Collections.Specialized)

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Microsoft Visual Studio 2005/.NET Framework 2.0

Other versions are also available for the following:

OrderedDictionary Class

Represents a collection of key/value pairs that are accessible by the key or index.

Namespace: System.Collections.Specialized
Assembly: System (in system.dll)

Syntax

Visual Basic (Declaration)

<SerializableAttribute> _
Public Class OrderedDictionary
    Implements IOrderedDictionary, IDictionary, ICollection, IEnumerable, _
    ISerializable, IDeserializationCallback

Visual Basic (Usage)

Dim instance As OrderedDictionary

[SerializableAttribute] 
public class OrderedDictionary : IOrderedDictionary, IDictionary, ICollection, 
    IEnumerable, ISerializable, IDeserializationCallback

C++

[SerializableAttribute] 
public ref class OrderedDictionary : IOrderedDictionary, IDictionary, ICollection, 
    IEnumerable, ISerializable, IDeserializationCallback

/** @attribute SerializableAttribute() */ 
public class OrderedDictionary implements IOrderedDictionary, IDictionary, 
    ICollection, IEnumerable, ISerializable, IDeserializationCallback

JScript

SerializableAttribute 
public class OrderedDictionary implements IOrderedDictionary, IDictionary, 
    ICollection, IEnumerable, ISerializable, IDeserializationCallback

XAML

Not applicable.

Remarks

Each element is a key/value pair stored in a DictionaryEntry object. A key cannot be a null reference (Nothing in Visual Basic), but a value can be.

The elements of an OrderedDictionary are not sorted in any way. OrderedDictionary collections allow access by both index as well as key.

The foreach statement of the C# language (For Each in Visual Basic) requires the type of each element in the collection. Since each element of the OrderedDictionary collection is a key/value pair, the element type is not the type of the key or the type of the value. Instead, the element type is DictionaryEntry. The following code shows C# and Visual Basic syntax.

foreach (DictionaryEntry de in myListDictionary) {...}

Visual Basic

For Each de As DictionaryEntry In myListDictionary
  ...
Next de

The foreach statement is a wrapper around the enumerator, which only allows reading from, not writing to, the collection.

Example

The following code example demonstrates the creation, population and modification of an OrderedDictionary collection, as well as two techniques to display the contents of the OrderedDictionary: one using the Keys and Values properties and the other creating an enumerator through the GetEnumerator method.

Visual Basic

' The following code example enumerates the elements of a OrderedDictionary.
Imports System
Imports System.Collections
Imports System.Collections.Specialized

Public Class OrderedDictionarySample

    Public Shared Sub Main()

        ' Creates and initializes a OrderedDictionary.
        Dim myOrderedDictionary As New OrderedDictionary()
        myOrderedDictionary.Add("testKey1", "testValue1")
        myOrderedDictionary.Add("testKey2", "testValue2")
        myOrderedDictionary.Add("keyToDelete", "valueToDelete")
        myOrderedDictionary.Add("testKey3", "testValue3")

        Dim keyCollection As ICollection = myOrderedDictionary.Keys
        Dim valueCollection As ICollection = myOrderedDictionary.Values

        ' Display the contents Imports the key and value collections
        DisplayContents( _
            keyCollection, valueCollection, myOrderedDictionary.Count)

        ' Modifying the OrderedDictionary
        If Not myOrderedDictionary.IsReadOnly Then

            ' 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")) Then
                myOrderedDictionary.Remove("keyToDelete")
            End If
        End If

        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 Imports an enumerator
        Dim myEnumerator As IDictionaryEnumerator = _
            myOrderedDictionary.GetEnumerator()

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

        DisplayEnumerator(myEnumerator)

        Console.ReadLine()
    End Sub

    ' Displays the contents of the OrderedDictionary from its keys and values
    Public Shared Sub DisplayContents( _
        ByVal keyCollection As ICollection, _
        ByVal valueCollection As ICollection, ByVal dictionarySize As Integer)

        Dim myKeys(dictionarySize) As [String]
        Dim myValues(dictionarySize) As [String]
        keyCollection.CopyTo(myKeys, 0)
        valueCollection.CopyTo(myValues, 0)

        ' Displays the contents of the OrderedDictionary
        Console.WriteLine("   INDEX KEY                       VALUE")
        Dim i As Integer
        For i = 0 To dictionarySize - 1
            Console.WriteLine("   {0,-5} {1,-25} {2}", _
                 i, myKeys(i), myValues(i))
        Next i
        Console.WriteLine()
    End Sub

    ' Displays the contents of the OrderedDictionary using its enumerator
    Public Shared Sub DisplayEnumerator( _
        ByVal myEnumerator As IDictionaryEnumerator)

        Console.WriteLine("   KEY                       VALUE")
        While myEnumerator.MoveNext()
            Console.WriteLine("   {0,-25} {1}", _
                myEnumerator.Key, myEnumerator.Value)
        End While
    End Sub
End Class

'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)

// 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

*/

Inheritance Hierarchy

System.Object
System.Collections.Specialized.OrderedDictionary
System.Web.Configuration.AdapterDictionary

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Platforms

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

Version Information

.NET Framework

Supported in: 3.0, 2.0

Reference

OrderedDictionary Members
System.Collections.Specialized Namespace