ListDictionary::Keys Property
Gets an ICollection containing the keys in the ListDictionary.
Assembly: System (in System.dll)
Property Value
Type: System.Collections::ICollection^An ICollection containing the keys in the ListDictionary.
Implements
IDictionary::KeysThe order of the values in the ICollection is unspecified, but it is the same order as the associated values in the ICollection returned by the Values method.
The returned ICollection is not a static copy; instead, the ICollection refers back to the keys in the original ListDictionary. Therefore, changes to the ListDictionary continue to be reflected in the ICollection.
Retrieving the value of this property is an O(1) operation.
The following code example enumerates the elements of a ListDictionary.
#using <System.dll> using namespace System; using namespace System::Collections; using namespace System::Collections::Specialized; void PrintKeysAndValues1( IDictionary^ myCol ); void PrintKeysAndValues2( IDictionary^ myCol ); void PrintKeysAndValues3( ListDictionary^ myCol ); int main() { // Creates and initializes a new ListDictionary. ListDictionary^ myCol = gcnew ListDictionary; myCol->Add( "Braeburn Apples", "1.49" ); myCol->Add( "Fuji Apples", "1.29" ); myCol->Add( "Gala Apples", "1.49" ); myCol->Add( "Golden Delicious Apples", "1.29" ); myCol->Add( "Granny Smith Apples", "0.89" ); myCol->Add( "Red Delicious Apples", "0.99" ); // 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 IDictionaryEnumerator:" ); 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 ); } // 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. void PrintKeysAndValues1( IDictionary^ myCol ) { Console::WriteLine( " KEY VALUE" ); for each ( DictionaryEntry^ de in myCol ) Console::WriteLine( " {0,-25} {1}", de->Key, de->Value ); Console::WriteLine(); } // Uses the enumerator. void PrintKeysAndValues2( IDictionary^ myCol ) { IDictionaryEnumerator^ myEnumerator = myCol->GetEnumerator(); Console::WriteLine( " KEY VALUE" ); while ( myEnumerator->MoveNext() ) Console::WriteLine( " {0,-25} {1}", myEnumerator->Key, myEnumerator->Value ); Console::WriteLine(); } // Uses the Keys, Values, Count, and Item properties. void PrintKeysAndValues3( ListDictionary^ myCol ) { array<String^>^myKeys = gcnew array<String^>(myCol->Count); myCol->Keys->CopyTo( myKeys, 0 ); Console::WriteLine( " INDEX KEY VALUE" ); for ( int i = 0; i < myCol->Count; i++ ) Console::WriteLine( " {0,-5} {1,-25} {2}", i, myKeys[ i ], myCol[ myKeys[ i ] ] ); Console::WriteLine(); } /* This code produces the following output. Displays the elements using for each: KEY VALUE Braeburn Apples 1.49 Fuji Apples 1.29 Gala Apples 1.49 Golden Delicious Apples 1.29 Granny Smith Apples 0.89 Red Delicious Apples 0.99 Displays the elements using the IDictionaryEnumerator: KEY VALUE Braeburn Apples 1.49 Fuji Apples 1.29 Gala Apples 1.49 Golden Delicious Apples 1.29 Granny Smith Apples 0.89 Red Delicious Apples 0.99 Displays the elements using the Keys, Values, Count, and Item properties: INDEX KEY VALUE 0 Braeburn Apples 1.49 1 Fuji Apples 1.29 2 Gala Apples 1.49 3 Golden Delicious Apples 1.29 4 Granny Smith Apples 0.89 5 Red Delicious Apples 0.99 */
Available since 10
.NET Framework
Available since 1.1