ListDictionary Constructor ()
.NET Framework (current version)
Creates an empty ListDictionary using the default comparer.
Assembly: System (in System.dll)
The comparer determines whether two keys are equal. Every key in a ListDictionary must be unique. The default comparer is the key's implementation of Object.Equals.
This constructor is an O(1) operation.
The following code example demonstrates several of the properties and methods of ListDictionary.
using System; using System.Collections; using System.Collections.Specialized; public class SamplesListDictionary { public static void Main() { // Creates and initializes a new ListDictionary. ListDictionary myCol = new 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 foreach. This is the preferred method. Console.WriteLine( "Displays the elements using foreach:" ); 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 ); // Copies the ListDictionary to an array with DictionaryEntry elements. DictionaryEntry[] myArr = new DictionaryEntry[myCol.Count]; myCol.CopyTo( myArr, 0 ); // Displays the values in the array. Console.WriteLine( "Displays the elements in the array:" ); Console.WriteLine( " KEY VALUE" ); for ( int i = 0; i < myArr.Length; i++ ) Console.WriteLine( " {0,-25} {1}", myArr[i].Key, myArr[i].Value ); Console.WriteLine(); // Searches for a key. if ( myCol.Contains( "Kiwis" ) ) Console.WriteLine( "The collection contains the key \"Kiwis\"." ); else Console.WriteLine( "The collection does not contain the key \"Kiwis\"." ); Console.WriteLine(); // Deletes a key. myCol.Remove( "Plums" ); Console.WriteLine( "The collection contains the following elements after removing \"Plums\":" ); PrintKeysAndValues1( myCol ); // Clears the entire collection. myCol.Clear(); Console.WriteLine( "The collection contains the following elements after it is cleared:" ); PrintKeysAndValues1( 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. public static void PrintKeysAndValues1( IDictionary myCol ) { Console.WriteLine( " KEY VALUE" ); foreach ( DictionaryEntry de in myCol ) Console.WriteLine( " {0,-25} {1}", de.Key, de.Value ); Console.WriteLine(); } // Uses the enumerator. // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection. public static 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. public static void PrintKeysAndValues3( ListDictionary myCol ) { String[] myKeys = new 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 output similar to the following. Note that because a dictionary is implemented for fast keyed access the order of the items in the dictionary are not gauranteed and, as a result, should not be depended on. Displays the elements using foreach: 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 Displays the elements in the array: 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 The collection does not contain the key "Kiwis". The collection contains the following elements after removing "Plums": 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 The collection contains the following elements after it is cleared: KEY VALUE */
Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
Available since 10
.NET Framework
Available since 1.1
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