CaseInsensitiveComparer Class

CaseInsensitiveComparer Class

 

Compares two objects for equivalence, ignoring the case of strings.

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

System::Object
  System.Collections::CaseInsensitiveComparer

[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class CaseInsensitiveComparer : IComparer

NameDescription
System_CAPS_pubmethodCaseInsensitiveComparer()

Initializes a new instance of the CaseInsensitiveComparer class using the Thread::CurrentCulture of the current thread.

System_CAPS_pubmethodCaseInsensitiveComparer(CultureInfo^)

Initializes a new instance of the CaseInsensitiveComparer class using the specified System.Globalization::CultureInfo.

NameDescription
System_CAPS_pubpropertySystem_CAPS_staticDefault

Gets an instance of CaseInsensitiveComparer that is associated with the Thread::CurrentCulture of the current thread and that is always available.

System_CAPS_pubpropertySystem_CAPS_staticDefaultInvariant

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

NameDescription
System_CAPS_pubmethodCompare(Object^, Object^)

Performs a case-insensitive comparison of two objects of the same type and returns a value indicating whether one is less than, equal to, or greater than the other.

System_CAPS_pubmethodEquals(Object^)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

CaseInsensitiveComparer implements the IComparer interface supporting case-insensitive comparisons on strings, just as CaseInsensitiveHashCodeProvider implements the IHashCodeProvider interface supporting case-insensitive comparisons on strings.

The Comparer class is the default implementation of the IComparer interface and performs case-sensitive string comparisons.

The objects used as keys by a Hashtable are required to override the Object::GetHashCode method (or the IHashCodeProvider interface) and the Object::Equals method (or the IComparer interface). The implementation of both methods or interfaces must handle case sensitivity the same way; otherwise, the Hashtable might behave incorrectly. For example, when creating a Hashtable, you must use this class with the CaseInsensitiveHashCodeProvider class or any case-insensitive IHashCodeProvider implementation.

String 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.

using namespace System;
using namespace System::Collections;
using namespace System::Globalization;
int main()
{

   // Create a Hashtable using the default hash code provider and the default comparer.
   Hashtable^ myHT1 = gcnew 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.
   Hashtable^ myHT2 = gcnew Hashtable( gcnew CaseInsensitiveHashCodeProvider,gcnew 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.
   Hashtable^ myHT3 = gcnew 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".
   CultureInfo^ myCul = gcnew CultureInfo( "tr-TR" );
   Hashtable^ myHT4 = gcnew Hashtable( gcnew CaseInsensitiveHashCodeProvider( myCul ),gcnew 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" ) );
}

/* 
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

*/

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

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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