????? ????? ?? ?????? HashTable ?? Visual Basic .NET ?? ?? Visual Basic 2005

???? ??? ??????? ??????? ??? ?????? HashTable. ??? ??????? ???? ?????? ????? ??????? ???????? ???????? ????????, ????? ??????? ??????? ???????? ???????? ???? ????. ????? ?????? ???? ??????? ???? ?????? ???? ????????.

???? "?????? ??? ?????" ??? HashTable ?? ????? ?? ????? ????? System.Collections ???? ?? ??? ???????? ??? ??????? ???????.

??????? ??????? ?????? ?? ?????

?????? HashTable ?????? ??? (????? ? ??????) ??????? ????? ??????? ??????? ??? ???? ???????. ????? immutable ??? ?? ???? ???? ??????? ????? ?? HashTable. ?????? ??? ??????? ??? ?????? ????? ????? ????? ?????? ?? HashTable. ??? ??????? ??? ??????? ??? ??? ?????.

1. ???? Microsoft Visual Studio .NET ?? Microsoft Visual Studio 2005 ?? ????? ????? ????? Windows ?? Visual Basic .NET ?? ?? Visual Basic 2005. ??? ????? Form1 ??? ??????? ???? ???????.
2. ?? "?????? ??????" ???? ??? ?????? ?????? ??? ??? ??????? ? ??? ??? ????? ? ?? ???? ??? ????? ??? ?????? ??? ???? ?????. ??? ????? Class1 ??? ??????? ???? ???????.
3. ?? ???? ?????? ????? ???? ???? ? ???? ??? ???.
   
   ?????? ?? Visual Studio 2005 ? ???? ??? ????? ????? ?? ???.
4. ?????? ??? ??????? ?????? ?? ?????? ??????? Class1 ???????? ???????? ???????:

   Public Class Person
       Public Fname, Lname As String
   
       Sub New(ByVal FirstName As String, ByVal LastName As String)
           Fname = FirstName
           Lname = LastName
       End Sub
   
       Public Overrides Function ToString() As String
           Return Fname + " " + Lname
       End Function
   End Class
   						

   ????? ??? ??????? ????? ???? ???? ???? ???????? ????? ????? "?" ??? ??????? ????? ?????? ??? ???????? ??? ????????? ???????. ?????? ?????? ToStringToString ?? ??? ???? ?????? FnameLname ?????? ????.
5. ?? Form1.vb ? ??? ????? ?????? ????????? ??????? ??? ???? ?????? ??????? ????????? ????????:

   Imports System.Collections
   					

6. ?? ?????? ???? ???? Hashtable ????? ??????? ?? ??????? ????? ????????? ?? ????? ?????. ?? ?????? ????????? ???????? ??????? ??? ??? Form1:

   Dim MyTable As New Hashtable()
   
   'For simplicity, create three Person objects to add to the HashTable collection.
   
   Dim Person1, Person2, Person3 As Person  
   					

7. ?? ??????? ??????? ??????? ??????? Add???? ???? Hashtable ????? ????? ?????? ????? ??? Hashtable ?? ???? ???????? catch. ???? ???????? catch catches ????????? ???? ????? ?? ???? ???? ?????? ?????.
   1. ??? ???? ???? ?? ??? Form1 ?????? ??????? Text ??? ????? ?????.
   2. ???? ????? ??????? ??? ???? ??? ???? ????????? ???????? ?????? ?? ?? ?? ???? ???????? ???????? ??????? ?? ????? Button1_Click:

      Person1 = New Person("Karen", "Berge")
      Person2 = New Person("David", "Campbell")
      Person3 = New Person("Jim", "Kim")
      
      'The Add method takes Key as the first parameter and Value as the second parameter.
      
      Try
           MyTable.Add(Person1.Lname, Person1)
           MyTable.Add(Person2.Lname, Person2)
           MyTable.Add(Person3.Lname, Person3)
      Catch ae As ArgumentException
           MessageBox.Show("Duplicate Key")
      End Try
      						

8. ???? ???? Hashtable ???? ?????. ?? ??????? ???????? ???? ??????? ?????? ??? ?????? ??????? ?? ?????? ???????.
   1. ????? ???? ???? ?? ??? Form1 ?????? ??????? Text ??? ????? ???????.
   2. ???? ????? ??????? ??? ???? ?? ?? ???? ???????? ???????? ??????? ?? ????? Button2_Click:

      'Use the indexer of the Hashtable class to retrieve your objects. The indexer takes 
      'Key as a parameter and accesses it with the Hashed location.
              
      Try
           MessageBox.Show(MyTable(Person1.Lname).ToString)
           MessageBox.Show(MyTable(Person2.Lname).ToString)
           MessageBox.Show(MyTable(Person3.Lname).ToString)
      Catch ex As NullReferenceException
           MessageBox.Show("Key not in Hashtable")
      End Try
      						

9. ?? ??????? ???????? ?????? ??????? ????? ?????? ???? ???? ?? ?????? HashTable:
   1. ????? ???? ???? ?? ??? Form1 ?????? ??????? Text ??? ????? ??????.
   2. ???? ????? ??????? ??? ???? ?? ?? ???? ???????? ???????? ??????? ?? ????? Button3_Click:

      'Use the Count property.
      If (MyTable.Count = 0) Then
           MessageBox.Show("There are no items in HashTable")
      Else
           MessageBox.Show("The count before removing an Item is" & " " & MyTable.Count)
           MessageBox.Show("Removing value stored at key value (Berge)")
           'Remove the object that is stored at the Key value Person1.Lname.
           MyTable.Remove(Person1.Lname)
      End If
      						

10. ?? ??????? ??????? ????? ??????? ???? ??? ??????? ?? ?????? HashTable.
    1. ????? ???? ???? ?? ??? Form1 ?????? ??????? Text ??? ???????.
    2. ???? ????? ??????? ??? ???? ?? ?? ???? ???????? ???????? ??????? ?? ????? Button4_Click:

       Dim Enumerator As IDictionaryEnumerator
       Enumerator = MyTable.GetEnumerator()
       
       If (MyTable.Count = 0) Then
            MessageBox.Show("The HashTable is empty")
       Else
            MessageBox.Show("Enumerating through the HashTable collection")
            While Enumerator.MoveNext()
                 MessageBox.Show(Enumerator.Value.ToString())
            End While
       End If
       
       Dim MyKeys As ICollection
       Dim Key As Object
       
       If (MyTable.Count = 0) Then
            MessageBox.Show("The HashTable is empty")
       Else
            MessageBox.Show("Accessing keys property to return keys collection")
            MyKeys = MyTable.Keys()
       
            For Each Key In MyKeys
                 MessageBox.Show(Key.ToString)
            Next
       End If 
       							

       ????????? ???????? ??? ??????? ?? ?????? ??? IDictionaryEnumerator ??? ???????? ??????? GetEnumerator ???????? HashTable. ?? ???? ????? ? ???????? ???????? ????? ???? ??????? ???????? ?? ???????? ??????? ????? ??????HashTable ????? ???? ????????.
11. ?? ??????? ???????? ?????? ??????? ??? ???? HashTable.
    1. ????? ???? ???? ?? ??? Form1 ?????? ??????? Text ??? ???.
    2. ???? ????? ??????? ??? ???? ?? ?? ???? ???????? ???????? ??????? ?? ????? Button5_Click:

       MyTable.Clear()
       MessageBox.Show("HashTable is now empty")
       						

12. ???? ??????? ??????? ?????? ??????? ???????:
    1. ???? ??? ????? ???????. ???? ?? ??? ????? ????? ?????? ????? ??? ???????? HashTable.
    2. ???? ??? ?????? ??? ???????. ???? ?? ??????? ???? ??? ??????? ???????? ?? ?????? HashTable. ????? ??????? ?????? ??? ??? ???????.
    3. ???? ??? ????? ??????. ???? ??? ??? ??? ?????? ?? ?????? "????" ???????.
    4. ???? ??? ?????. ???? ????? IDictionaryEnumerator ???? ??????? ???????? ?? ?????? HashTable.
    5. ???? ??? ???. ???? ?? ??? ??? ???? ??????? ?? ?????? HashTable.

??????: ??????? ? ???????? ? ?????? ? ????? ?????? ? ?????? ?????? ?????????? ? ???????? ? ???????, ? ???????? ?????? ????? ??? ?????? ?????. ?? ????? ?? ???? ? ??????? ? ??????, ??? ?????? ? ????? ?????? ?????????? ? ???? ? ????? ?? ????? ?? ????? ?? ??? ??? ??????? ??? ?????? ?? ??? ?????.