HybridDictionary::Item Property (Object^)
Gets or sets the value associated with the specified key.
Assembly: System (in System.dll)
public: property Object^ default[ Object^ key ] { virtual Object^ get(Object^ key) sealed; virtual void set(Object^ key, Object^ value) sealed; }
Parameters
- key
-
Type:
System::Object^
The key whose value to get or set.
Property Value
Type: System::Object^The value associated with the specified key. If the specified key is not found, attempting to get it returns null, and attempting to set it creates a new entry using the specified key.
Implements
IDictionary::Item[Object^]| Exception | Condition |
|---|---|
| ArgumentNullException | key is null. |
This property provides the ability to access a specific element in the collection by using the following syntax: myCollection[key].
You can also use the Item property to add new elements by setting the value of a key that does not exist in the HybridDictionary; for example, myCollection["myNonexistentKey"] = myValue. However, if the specified key already exists in the HybridDictionary, setting the Item property overwrites the old value. In contrast, the Add method does not modify existing elements.
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 Contains 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 HybridDictionary.
#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( HybridDictionary^ myCol ); int main() { // Creates and initializes a new HybridDictionary. HybridDictionary^ myCol = gcnew HybridDictionary; 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" ); myCol->Add( "Plantain Bananas", "1.49" ); myCol->Add( "Yellow Bananas", "0.79" ); myCol->Add( "Strawberries", "3.33" ); myCol->Add( "Cranberries", "5.98" ); myCol->Add( "Navel Oranges", "1.29" ); myCol->Add( "Grapes", "1.99" ); myCol->Add( "Honeydew Melon", "0.59" ); myCol->Add( "Seedless Watermelon", "0.49" ); myCol->Add( "Pineapple", "1.49" ); myCol->Add( "Nectarine", "1.99" ); myCol->Add( "Plums", "1.69" ); myCol->Add( "Peaches", "1.99" ); // 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 foreach statement which hides the complexity of the enumerator. // NOTE: The foreach 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( HybridDictionary^ 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 Seedless Watermelon 0.49 Nectarine 1.99 Cranberries 5.98 Plantain Bananas 1.49 Honeydew Melon 0.59 Pineapple 1.49 Strawberries 3.33 Grapes 1.99 Braeburn Apples 1.49 Peaches 1.99 Red Delicious Apples 0.99 Golden Delicious Apples 1.29 Yellow Bananas 0.79 Granny Smith Apples 0.89 Gala Apples 1.49 Plums 1.69 Navel Oranges 1.29 Fuji Apples 1.29 Displays the elements using the IDictionaryEnumerator: KEY VALUE Seedless Watermelon 0.49 Nectarine 1.99 Cranberries 5.98 Plantain Bananas 1.49 Honeydew Melon 0.59 Pineapple 1.49 Strawberries 3.33 Grapes 1.99 Braeburn Apples 1.49 Peaches 1.99 Red Delicious Apples 0.99 Golden Delicious Apples 1.29 Yellow Bananas 0.79 Granny Smith Apples 0.89 Gala Apples 1.49 Plums 1.69 Navel Oranges 1.29 Fuji Apples 1.29 Displays the elements using the Keys, Values, Count, and Item properties: INDEX KEY VALUE 0 Seedless Watermelon 0.49 1 Nectarine 1.99 2 Cranberries 5.98 3 Plantain Bananas 1.49 4 Honeydew Melon 0.59 5 Pineapple 1.49 6 Strawberries 3.33 7 Grapes 1.99 8 Braeburn Apples 1.49 9 Peaches 1.99 10 Red Delicious Apples 0.99 11 Golden Delicious Apples 1.29 12 Yellow Bananas 0.79 13 Granny Smith Apples 0.89 14 Gala Apples 1.49 15 Plums 1.69 16 Navel Oranges 1.29 17 Fuji Apples 1.29 */
Available since 10
.NET Framework
Available since 1.1