Dictionary<TKey, TValue> Class

Type Parameters

• TKey
  The type of the keys in the dictionary.

• TValue
  The type of the values in the dictionary.

Public Class OthelloCast
    Inherits List(Of String)

    Public OthelloDict As New Dictionary(Of String, String)

    Public Sub New()

        ' Add data to the dictionary.
        OthelloDict.Add("Bianca", "Gretchen Rivas")
        OthelloDict.Add("Brabantio", "Carlos Lacerda")
        OthelloDict.Add("Cassio", "Steve Masters")
        OthelloDict.Add("Clown", "Michael Ludwig")
        OthelloDict.Add("Desdemona", "Catherine Autier Miconi")
        OthelloDict.Add("Duke of Venice", "Ken Circeo")
        OthelloDict.Add("Emilia", "Eva Valverde")
        OthelloDict.Add("Gratiano", "Akos Kozari")
        OthelloDict.Add("Iago", "Darius Stasevicius")
        OthelloDict.Add("Lodovico", "Fernando Souza")
        OthelloDict.Add("Montano", "Jeff Hay")
        OthelloDict.Add("Othello", "Marco Tanara")
        OthelloDict.Add("Roderigo", "Pedro Ruivo")

        ' Populate the list with character names.
        For Each kvp As KeyValuePair(Of String, String) In OthelloDict
            Me.Add(kvp.Key)
        Next
    End Sub
End Class

// Make sure this class is
// within the C# namespace.
public class OthelloCast : List<string>
{
    // Use a dictionary to contain
    // cast names (key) and actor names (value).
    public Dictionary<string, string> OthelloDict =
        new Dictionary<string, string>();

    public OthelloCast()
    {
        // Add data to the dictionary.
        OthelloDict.Add("Bianca", "Gretchen Rivas");
        OthelloDict.Add("Brabantio", "Carlos Lacerda");
        OthelloDict.Add("Cassio", "Steve Masters");
        OthelloDict.Add("Clown", "Michael Ludwig");
        OthelloDict.Add("Desdemona", "Catherine Autier Miconi");
        OthelloDict.Add("Duke of Venice", "Ken Circeo");
        OthelloDict.Add("Emilia", "Eva Valverde");
        OthelloDict.Add("Gratiano", "Akos Kozari");
        OthelloDict.Add("Iago", "Darius Stasevicius");
        OthelloDict.Add("Lodovico", "Fernando Souza");
        OthelloDict.Add("Montano", "Jeff Hay");
        OthelloDict.Add("Othello", "Marco Tanara");
        OthelloDict.Add("Roderigo", "Pedro Ruivo");

        // Populate the list with character names.
        foreach (KeyValuePair<string, string> kvp in OthelloDict)
        {
            this.Add(kvp.Key);
        }
    }
}

Private Sub ListCharacters_SelectionChanged(ByVal sender As System.Object, ByVal e As SelectionChangedEventArgs)
    ' Create an instance of OthelloCast to
    ' look up an actor by their character.
    Dim othello As New OthelloCast()

    ' Get the selected character name (key).
    Dim key As String = ListCharacters.SelectedItem.ToString()

    ' Get the key's value (actor name) and display it.
    ShowActor.Text = othello.OthelloDict(key).ToString()
End Sub

private void ListCharacters_SelectionChanged(object sender,
    SelectionChangedEventArgs e)
{
    // Create an instance of OthelloCast to
    // look up an actor by their character.
    OthelloCast othello = new OthelloCast();

    // Get the selected character name (key).
    string key = ListCharacters.SelectedItem.ToString();

    // Get the key's value (actor name) and display it.
    ShowActor.Text = othello.OthelloDict[key].ToString();
}

 <UserControl x:Class="CastMembers.Page"
    xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:my="clr-namespace:CastMembers"
    Width="400" Height="400">
    <Grid x:Name="LayoutRoot" Background="White" ShowGridLines="False">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Grid.Resources>
            <my:OthelloCast x:Name="Characters"/>
        </Grid.Resources>
        <TextBlock Margin ="5,5,5,5" Grid.Row="0" Grid.Column="0" Text="Othello Cast:" FontWeight="Bold" />
        <ListBox Margin ="5,5,5,5" SelectionChanged="ListCharacters_SelectionChanged" Grid.Row="1" Grid.Column="0" x:Name="ListCharacters"  ItemsSource="{Binding Source={StaticResource Characters}}"/>
        <TextBlock Margin ="5,5,5,5" Grid.Row="0" Grid.Column="1" Text="Actor:" FontWeight="Bold" />
        <TextBlock Margin ="5,5,5,5" Grid.Row="1" Grid.Column="1" x:Name="ShowActor" Text=""/> 
    </Grid>
</UserControl>

Imports System.Collections.Generic

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Create a new dictionary of strings, with string keys.
      '
      Dim openWith As New Dictionary(Of String, String)

      ' Add some elements to the dictionary. There are no 
      ' duplicate keys, but some of the values are duplicates.
      openWith.Add("txt", "notepad.exe")
      openWith.Add("bmp", "paint.exe")
      openWith.Add("dib", "paint.exe")
      openWith.Add("rtf", "wordpad.exe")

      ' The Add method throws an exception if the new key is 
      ' already in the dictionary.
      Try
         openWith.Add("txt", "winword.exe")
      Catch
         outputBlock.Text &= "An element with Key = ""txt"" already exists." & vbCrLf
      End Try

      ' The Item property is the default property, so you 
      ' can omit its name when accessing elements. 
      outputBlock.Text &= String.Format("For key = ""rtf"", value = {0}.", _
          openWith("rtf")) & vbCrLf

      ' The default Item property can be used to change the value
      ' associated with a key.
      openWith("rtf") = "winword.exe"
      outputBlock.Text &= String.Format("For key = ""rtf"", value = {0}.", _
          openWith("rtf")) & vbCrLf

      ' If a key does not exist, setting the default Item property
      ' for that key adds a new key/value pair.
      openWith("doc") = "winword.exe"

      ' The default Item property throws an exception if the requested
      ' key is not in the dictionary.
      Try
         outputBlock.Text &= String.Format("For key = ""tif"", value = {0}.", _
             openWith("tif")) & vbCrLf
      Catch
         outputBlock.Text &= "Key = ""tif"" is not found." & vbCrLf
      End Try

      ' When a program often has to try keys that turn out not to
      ' be in the dictionary, TryGetValue can be a more efficient 
      ' way to retrieve values.
      Dim value As String = ""
      If openWith.TryGetValue("tif", value) Then
         outputBlock.Text &= String.Format("For key = ""tif"", value = {0}.", value) & vbCrLf
      Else
         outputBlock.Text &= "Key = ""tif"" is not found." & vbCrLf
      End If

      ' ContainsKey can be used to test keys before inserting 
      ' them.
      If Not openWith.ContainsKey("ht") Then
         openWith.Add("ht", "hypertrm.exe")
         outputBlock.Text &= String.Format("Value added for key = ""ht"": {0}", _
             openWith("ht")) & vbCrLf
      End If

      ' When you use foreach to enumerate dictionary elements,
      ' the elements are retrieved as KeyValuePair objects.
      outputBlock.Text &= vbCrLf
      For Each kvp As KeyValuePair(Of String, String) In openWith
         outputBlock.Text &= String.Format("Key = {0}, Value = {1}", _
             kvp.Key, kvp.Value) & vbCrLf
      Next kvp

      ' To get the values alone, use the Values property.
      Dim valueColl As  _
          Dictionary(Of String, String).ValueCollection = _
          openWith.Values

      ' The elements of the ValueCollection are strongly typed
      ' with the type that was specified for dictionary values.
      outputBlock.Text &= vbCrLf
      For Each s As String In valueColl
         outputBlock.Text &= String.Format("Value = {0}", s) & vbCrLf
      Next s

      ' To get the keys alone, use the Keys property.
      Dim keyColl As  _
          Dictionary(Of String, String).KeyCollection = _
          openWith.Keys

      ' The elements of the KeyCollection are strongly typed
      ' with the type that was specified for dictionary keys.
      outputBlock.Text &= vbCrLf
      For Each s As String In keyColl
         outputBlock.Text &= String.Format("Key = {0}", s) & vbCrLf
      Next s

      ' Use the Remove method to remove a key/value pair.
      outputBlock.Text &= vbLf + "Remove(""doc"")" & vbCrLf
      openWith.Remove("doc")

      If Not openWith.ContainsKey("doc") Then
         outputBlock.Text &= "Key ""doc"" is not found." & vbCrLf
      End If

   End Sub

End Class

' This code example produces the following output:
'
'An element with Key = "txt" already exists.
'For key = "rtf", value = wordpad.exe.
'For key = "rtf", value = winword.exe.
'Key = "tif" is not found.
'Key = "tif" is not found.
'Value added for key = "ht": hypertrm.exe
'
'Key = txt, Value = notepad.exe
'Key = bmp, Value = paint.exe
'Key = dib, Value = paint.exe
'Key = rtf, Value = winword.exe
'Key = doc, Value = winword.exe
'Key = ht, Value = hypertrm.exe
'
'Value = notepad.exe
'Value = paint.exe
'Value = paint.exe
'Value = winword.exe
'Value = winword.exe
'Value = hypertrm.exe
'
'Key = txt
'Key = bmp
'Key = dib
'Key = rtf
'Key = doc
'Key = ht
'
'Remove("doc")
'Key "doc" is not found.
' 

using System;
using System.Collections.Generic;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create a new dictionary of strings, with string keys.
      //
      Dictionary<string, string> openWith =
          new Dictionary<string, string>();

      // Add some elements to the dictionary. There are no 
      // duplicate keys, but some of the values are duplicates.
      openWith.Add("txt", "notepad.exe");
      openWith.Add("bmp", "paint.exe");
      openWith.Add("dib", "paint.exe");
      openWith.Add("rtf", "wordpad.exe");

      // The Add method throws an exception if the new key is 
      // already in the dictionary.
      try
      {
         openWith.Add("txt", "winword.exe");
      }
      catch (ArgumentException)
      {
         outputBlock.Text += "An element with Key = \"txt\" already exists." + "\n";
      }

      // The Item property is another name for the indexer, so you 
      // can omit its name when accessing elements. 
      outputBlock.Text += String.Format("For key = \"rtf\", value = {0}.",
          openWith["rtf"]) + "\n";

      // The indexer can be used to change the value associated
      // with a key.
      openWith["rtf"] = "winword.exe";
      outputBlock.Text += String.Format("For key = \"rtf\", value = {0}.",
          openWith["rtf"]) + "\n";

      // If a key does not exist, setting the indexer for that key
      // adds a new key/value pair.
      openWith["doc"] = "winword.exe";

      // The indexer throws an exception if the requested key is
      // not in the dictionary.
      try
      {
         outputBlock.Text += String.Format("For key = \"tif\", value = {0}.",
             openWith["tif"]) + "\n";
      }
      catch (KeyNotFoundException)
      {
         outputBlock.Text += "Key = \"tif\" is not found." + "\n";
      }

      // When a program often has to try keys that turn out not to
      // be in the dictionary, TryGetValue can be a more efficient 
      // way to retrieve values.
      string value = "";
      if (openWith.TryGetValue("tif", out value))
      {
         outputBlock.Text += String.Format("For key = \"tif\", value = {0}.", value) + "\n";
      }
      else
      {
         outputBlock.Text += "Key = \"tif\" is not found." + "\n";
      }

      // ContainsKey can be used to test keys before inserting 
      // them.
      if (!openWith.ContainsKey("ht"))
      {
         openWith.Add("ht", "hypertrm.exe");
         outputBlock.Text += String.Format("Value added for key = \"ht\": {0}",
             openWith["ht"]) + "\n";
      }

      // When you use foreach to enumerate dictionary elements,
      // the elements are retrieved as KeyValuePair objects.
      outputBlock.Text += "\n";
      foreach (KeyValuePair<string, string> kvp in openWith)
      {
         outputBlock.Text += String.Format("Key = {0}, Value = {1}",
             kvp.Key, kvp.Value) + "\n";
      }

      // To get the values alone, use the Values property.
      Dictionary<string, string>.ValueCollection valueColl =
          openWith.Values;

      // The elements of the ValueCollection are strongly typed
      // with the type that was specified for dictionary values.
      outputBlock.Text += "\n";
      foreach (string s in valueColl)
      {
         outputBlock.Text += String.Format("Value = {0}", s) + "\n";
      }

      // To get the keys alone, use the Keys property.
      Dictionary<string, string>.KeyCollection keyColl =
          openWith.Keys;

      // The elements of the KeyCollection are strongly typed
      // with the type that was specified for dictionary keys.
      outputBlock.Text += "\n";
      foreach (string s in keyColl)
      {
         outputBlock.Text += String.Format("Key = {0}", s) + "\n";
      }

      // Use the Remove method to remove a key/value pair.
      outputBlock.Text += "\nRemove(\"doc\")" + "\n";
      openWith.Remove("doc");

      if (!openWith.ContainsKey("doc"))
      {
         outputBlock.Text += "Key \"doc\" is not found." + "\n";
      }
   }
}

/* This code example produces the following output:

An element with Key = "txt" already exists.
For key = "rtf", value = wordpad.exe.
For key = "rtf", value = winword.exe.
Key = "tif" is not found.
Key = "tif" is not found.
Value added for key = "ht": hypertrm.exe

Key = txt, Value = notepad.exe
Key = bmp, Value = paint.exe
Key = dib, Value = paint.exe
Key = rtf, Value = winword.exe
Key = doc, Value = winword.exe
Key = ht, Value = hypertrm.exe

Value = notepad.exe
Value = paint.exe
Value = paint.exe
Value = winword.exe
Value = winword.exe
Value = hypertrm.exe

Key = txt
Key = bmp
Key = dib
Key = rtf
Key = doc
Key = ht

Remove("doc")
Key "doc" is not found.
 */