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HybridDictionary.Add Method

Adds an entry with the specified key and value into the HybridDictionary.

Namespace: System.Collections.Specialized
Assembly: System (in system.dll)

public void Add (
	Object key,
	Object value
)
public final void Add (
	Object key, 
	Object value
)
public final function Add (
	key : Object, 
	value : Object
)
Not applicable.

Parameters

key

The key of the entry to add.

value

The value of the entry to add. The value can be a null reference (Nothing in Visual Basic).

Exception typeCondition

ArgumentNullException

key is a null reference (Nothing in Visual Basic).

ArgumentException

An entry with the same key already exists in the HybridDictionary.

An object that has no correlation between its state and its hash code value should typically not be used as the key. For example, String objects are better than StringBuilder objects for use as keys.

A key cannot be a null reference (Nothing in Visual Basic), but a value can.

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.

When the number of elements becomes greater than the optimal size for a ListDictionary, the elements are copied from the ListDictionary to a Hashtable. However, this only happens once. If the collection is already stored in a Hashtable and the number of elements falls below the optimal size for a ListDictionary, the collection remains in the Hashtable.

This method is an O(1) operation.

The following code example adds to and removes elements from a HybridDictionary.

using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesHybridDictionary  {

   public static void Main()  {

      // Creates and initializes a new HybridDictionary.
      HybridDictionary myCol = new 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" );

      // Displays the values in the HybridDictionary in three different ways.
      Console.WriteLine( "Initial contents of the HybridDictionary:" );
      PrintKeysAndValues( myCol );

      // Deletes a key.
      myCol.Remove( "Plums" );
      Console.WriteLine( "The collection contains the following elements after removing \"Plums\":" );
      PrintKeysAndValues( myCol );

      // Clears the entire collection.
      myCol.Clear();
      Console.WriteLine( "The collection contains the following elements after it is cleared:" );
      PrintKeysAndValues( myCol );

   }

   public static void PrintKeysAndValues( IDictionary myCol )  {
      Console.WriteLine( "   KEY                       VALUE" );
      foreach ( DictionaryEntry de in myCol )
         Console.WriteLine( "   {0,-25} {1}", de.Key, de.Value );
      Console.WriteLine();
   }

}

/*
This code produces the following output.

Initial contents of the HybridDictionary:
   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

The collection contains the following elements after removing "Plums":
   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
   Navel Oranges             1.29
   Fuji Apples               1.29

The collection contains the following elements after it is cleared:
   KEY                       VALUE

*/

import System.*;
import System.Collections.*;
import System.Collections.Specialized.*;

public class SamplesHybridDictionary
{
    public static void main(String[] args)
    {
        // Creates and initializes a new HybridDictionary.
        HybridDictionary myCol = new 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");
          
        // Displays the values in the HybridDictionary in three different ways.
        Console.WriteLine("Initial contents of the HybridDictionary:");
        PrintKeysAndValues(myCol);
          
        // Deletes a key.
        myCol.Remove("Plums");
        Console.WriteLine("The collection contains the following elements"
            + " after removing \"Plums\":");
        PrintKeysAndValues(myCol);
          
        // Clears the entire collection.
        myCol.Clear();
        Console.WriteLine("The collection contains the following elements"
            + " after it is cleared:");
        PrintKeysAndValues(myCol);
   } //main    
   
   public static void PrintKeysAndValues(IDictionary myCol) 
   {
        IEnumerator objEnum = myCol.GetEnumerator();
        Console.WriteLine("   KEY                       VALUE");
        while (objEnum.MoveNext()) {
            DictionaryEntry de = (DictionaryEntry)objEnum.get_Current();
            Console.WriteLine("   {0,-25} {1}", de.get_Key(), de.get_Value());
        }
        Console.WriteLine();
    } //PrintKeysAndValues
} //SamplesHybridDictionary
 
/*
This code produces the following output.

Initial contents of the HybridDictionary:
   KEY                       VALUE
   Strawberries              3.33
   Yellow Bananas            0.79
   Cranberries               5.98
   Grapes                    1.99
   Granny Smith Apples       0.89
   Seedless Watermelon       0.49
   Honeydew Melon            0.59
   Red Delicious Apples      0.99
   Navel Oranges             1.29
   Fuji Apples               1.29
   Plantain Bananas          1.49
   Gala Apples               1.49
   Pineapple                 1.49
   Plums                     1.69
   Braeburn Apples           1.49
   Peaches                   1.99
   Golden Delicious Apples   1.29
   Nectarine                 1.99

The collection contains the following elements after removing "Plums":
   KEY                       VALUE
   Strawberries              3.33
   Yellow Bananas            0.79
   Cranberries               5.98
   Grapes                    1.99
   Granny Smith Apples       0.89
   Seedless Watermelon       0.49
   Honeydew Melon            0.59
   Red Delicious Apples      0.99
   Navel Oranges             1.29
   Fuji Apples               1.29
   Plantain Bananas          1.49
   Gala Apples               1.49
   Pineapple                 1.49
   Braeburn Apples           1.49
   Peaches                   1.99
   Golden Delicious Apples   1.29
   Nectarine                 1.99

The collection contains the following elements after it is cleared:
   KEY                       VALUE

*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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