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CaseInsensitiveHashCodeProvider.DefaultInvariant Property

Gets an instance of CaseInsensitiveHashCodeProvider that is associated with CultureInfo.InvariantCulture and that is always available.

Namespace:  System.Collections
Assembly:  mscorlib (in mscorlib.dll)
Public Shared ReadOnly Property DefaultInvariant As CaseInsensitiveHashCodeProvider

Comparison procedures use the CultureInfo.InvariantCulture to determine the casing rules. Hash code comparisons might have different results depending on the culture. For more information on culture-specific comparisons, see the System.Globalization namespace and Globalizing and Localizing .NET Framework Applications.

The following code example creates a case-sensitive hash table and a case-insensitive hash table and demonstrates the difference in their behavior, even if both contain the same elements.

Imports System
Imports System.Collections
Imports System.Globalization

Public Class SamplesHashtable

   Public Shared Sub Main()

      ' Create a Hashtable using the default hash code provider and the default comparer. 
      Dim myHT1 As New Hashtable()
      myHT1.Add("FIRST", "Hello")
      myHT1.Add("SECOND", "World")
      myHT1.Add("THIRD", "!")

      ' Create a Hashtable using a case-insensitive code provider and a case-insensitive comparer, 
      ' based on the culture of the current thread. 
      Dim myHT2 As New Hashtable(New CaseInsensitiveHashCodeProvider(), New CaseInsensitiveComparer())
      myHT2.Add("FIRST", "Hello")
      myHT2.Add("SECOND", "World")
      myHT2.Add("THIRD", "!")

      ' Create a Hashtable using a case-insensitive code provider and a case-insensitive comparer, 
      ' based on the InvariantCulture. 
      Dim myHT3 As New Hashtable(CaseInsensitiveHashCodeProvider.DefaultInvariant, CaseInsensitiveComparer.DefaultInvariant)
      myHT3.Add("FIRST", "Hello")
      myHT3.Add("SECOND", "World")
      myHT3.Add("THIRD", "!")

      ' Create a Hashtable using a case-insensitive code provider and a case-insensitive comparer, 
      ' based on the Turkish culture (tr-TR), where "I" is not the uppercase version of "i". 
      Dim myCul As New CultureInfo("tr-TR")
      Dim myHT4 As New Hashtable(New CaseInsensitiveHashCodeProvider(myCul), New CaseInsensitiveComparer(myCul))
      myHT4.Add("FIRST", "Hello")
      myHT4.Add("SECOND", "World")
      myHT4.Add("THIRD", "!")

      ' Search for a key in each hashtable.
      Console.WriteLine("first is in myHT1: {0}", myHT1.ContainsKey("first"))
      Console.WriteLine("first is in myHT2: {0}", myHT2.ContainsKey("first"))
      Console.WriteLine("first is in myHT3: {0}", myHT3.ContainsKey("first"))
      Console.WriteLine("first is in myHT4: {0}", myHT4.ContainsKey("first"))

   End Sub 'Main 

End Class 'SamplesHashtable

'This code produces the following output.  Results vary depending on the system's culture settings. 

'first is in myHT1: False 
'first is in myHT2: True 
'first is in myHT3: True 
'first is in myHT4: False

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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