StringDictionary.ContainsKey Method (String)


Determines if the StringDictionary contains a specific key.

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

Public Overridable Function ContainsKey (
	key As String
) As Boolean


Type: System.String

The key to locate in the StringDictionary.

Return Value

Type: System.Boolean

true if the StringDictionary contains an entry with the specified key; otherwise, false.

Exception Condition

The key is null.

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

This method is an O(1) operation.

Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.

The following code example searches for an element in 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")

      ' Displays the values in the StringDictionary.
      Console.WriteLine("Initial contents of the StringDictionary:")

      ' Searches for a key.
      If myCol.ContainsKey("red") Then
         Console.WriteLine("The collection contains the key ""red"".")
         Console.WriteLine("The collection does not contain the key ""red"".")
      End If

      ' Searches for a value.
      If myCol.ContainsValue("amarillo") Then
         Console.WriteLine("The collection contains the value ""amarillo"".")
         Console.WriteLine("The collection does not contain the value ""amarillo"".")
      End If

   End Sub 'Main

   Public Shared Sub PrintKeysAndValues(myCol As StringDictionary)
      Dim de As DictionaryEntry

      Console.WriteLine("   KEY        VALUE")
      For Each de In  myCol
         Console.WriteLine("   {0,-10} {1}", de.Key, de.Value)
      Next de

   End Sub 'PrintKeysAndValues

End Class 'SamplesStringDictionary 

'This code produces the following output.
'Initial contents of the StringDictionary:
'   KEY        VALUE
'   green      verde
'   red        rojo
'   blue       azul
'The collection contains the key "red".
'The collection does not contain the value "amarillo".

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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