Item Property
Collapse the table of content
Expand the table of content

StringDictionary.Item Property (String)

 

Gets or sets the value associated with the specified key.

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

Public Overridable Property Item (
	key As String
) As String

Parameters

key
Type: System.String

The key whose value to get or set.

Property Value

Type: System.String

The value associated with the specified key. If the specified key is not found, Get returns null, and Set creates a new entry with the specified key.

Exception Condition
ArgumentNullException

key is null.

The key is handled in a case-insensitive manner; it is translated to lowercase before it is used.

A key cannot be null, but a value can. To distinguish between null that is returned because the specified key is not found and null that is returned because the value of the specified key is null, use the ContainsKey method to determine if the key exists in the list.

The C# language uses the keyword to define the indexers instead of implementing the Item property. Visual Basic implements Item as a default property, which provides the same indexing functionality.

Retrieving the value of this property is an O(1) operation; setting the property is also an O(1) operation.

The following code example enumerates the elements of a StringDictionary.

Imports System
Imports System.Collections
Imports System.Collections.Specialized

Public Class SamplesStringDictionary

   Public Shared Sub Main()

      ' Creates and initializes a new StringDictionary.
      Dim myCol As New StringDictionary()
      myCol.Add("red", "rojo")
      myCol.Add("green", "verde")
      myCol.Add("blue", "azul")

      ' Display the contents of the collection using For Each. This is the preferred method.
      Console.WriteLine("Displays the elements using For Each:")
      PrintKeysAndValues1(myCol)

      ' Display the contents of the collection using the enumerator.
      Console.WriteLine("Displays the elements using the IEnumerator:")
      PrintKeysAndValues2(myCol)

      ' Display the contents of the collection using the Keys, Values, Count, and Item properties.
      Console.WriteLine("Displays the elements using the Keys, Values, Count, and Item properties:")
      PrintKeysAndValues3(myCol)

   End Sub 'Main


   ' Uses the For Each statement which hides the complexity of the enumerator.
   ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
   Public Shared Sub PrintKeysAndValues1(myCol As StringDictionary)
      Console.WriteLine("   KEY                       VALUE")
      Dim de As DictionaryEntry
      For Each de In  myCol
         Console.WriteLine("   {0,-25} {1}", de.Key, de.Value)
      Next de
      Console.WriteLine()
   End Sub 'PrintKeysAndValues1


   ' Uses the enumerator. 
   ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
   Public Shared Sub PrintKeysAndValues2(myCol As StringDictionary)
      Dim myEnumerator As IEnumerator = myCol.GetEnumerator()
      Dim de As DictionaryEntry
      Console.WriteLine("   KEY                       VALUE")
      While myEnumerator.MoveNext()
         de = CType(myEnumerator.Current, DictionaryEntry)
         Console.WriteLine("   {0,-25} {1}", de.Key, de.Value)
      End While
      Console.WriteLine()
   End Sub 'PrintKeysAndValues2


   ' Uses the Keys, Values, Count, and Item properties.
   Public Shared Sub PrintKeysAndValues3(myCol As StringDictionary)
      Dim myKeys(myCol.Count) As String
      myCol.Keys.CopyTo(myKeys, 0)

      Console.WriteLine("   INDEX KEY                       VALUE")
      Dim i As Integer
      For i = 0 To myCol.Count - 1
         Console.WriteLine("   {0,-5} {1,-25} {2}", i, myKeys(i), myCol(myKeys(i)))
      Next i
      Console.WriteLine()
   End Sub 'PrintKeysAndValues3

End Class 'SamplesStringDictionary 


'This code produces the following output.
'
'Displays the elements using For Each:
'   KEY                       VALUE
'   red                       rojo
'   blue                      azul
'   green                     verde
'
'Displays the elements using the IEnumerator:
'   KEY                       VALUE
'   red                       rojo
'   blue                      azul
'   green                     verde
'
'Displays the elements using the Keys, Values, Count, and Item properties:
'   INDEX KEY                       VALUE
'   0     red                       rojo
'   1     blue                      azul
'   2     green                     verde

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
Return to top
Show:
© 2016 Microsoft