Hashtable.Add(Object, Object) Método

Definición

Agrega un elemento con la clave y el valor especificados a Hashtable.Adds an element with the specified key and value into the Hashtable.

public:
 virtual void Add(System::Object ^ key, System::Object ^ value);
public virtual void Add (object key, object value);
public virtual void Add (object key, object? value);
abstract member Add : obj * obj -> unit
override this.Add : obj * obj -> unit
Public Overridable Sub Add (key As Object, value As Object)

Parámetros

key
Object

Clave del elemento que se va a agregar.The key of the element to add.

value
Object

Valor del elemento que se va a agregar.The value of the element to add. El valor puede ser null.The value can be null.

Implementaciones

Excepciones

key es null.key is null.

Ya existe un elemento con la misma clave en Hashtable.An element with the same key already exists in the Hashtable.

Hashtable es de solo lectura.The Hashtable is read-only.

o bien-or- Hashtable tiene un tamaño fijo.The Hashtable has a fixed size.

Ejemplos

En el ejemplo siguiente se muestra cómo agregar elementos a Hashtable .The following example shows how to add elements to the Hashtable.

using namespace System;
using namespace System::Collections;
void PrintKeysAndValues( Hashtable^ myHT );
int main()
{
   
   // Creates and initializes a new Hashtable.
   Hashtable^ myHT = gcnew Hashtable;
   myHT->Add( "one", "The" );
   myHT->Add( "two", "quick" );
   myHT->Add( "three", "brown" );
   myHT->Add( "four", "fox" );
   
   // Displays the Hashtable.
   Console::WriteLine( "The Hashtable contains the following:" );
   PrintKeysAndValues( myHT );
}

void PrintKeysAndValues( Hashtable^ myHT )
{
   Console::WriteLine( "\t-KEY-\t-VALUE-" );
   IEnumerator^ myEnum = myHT->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      DictionaryEntry de = *safe_cast<DictionaryEntry ^>(myEnum->Current);
      Console::WriteLine( "\t{0}:\t{1}", de.Key, de.Value );
   }

   Console::WriteLine();
}

/* 
 This code produces the following output.
 
 The Hashtable contains the following:
         -KEY-   -VALUE-
         two:    quick
         three:  brown
         four:   fox
         one:    The
 */
using System;
using System.Collections;
public class SamplesHashtable
{

   public static void Main()
   {
      // Creates and initializes a new Hashtable.
      var myHT = new Hashtable();
      myHT.Add("one", "The");
      myHT.Add("two", "quick");
      myHT.Add("three", "brown");
      myHT.Add("four", "fox");

      // Displays the Hashtable.
      Console.WriteLine("The Hashtable contains the following:");
      PrintKeysAndValues(myHT);
   }

   public static void PrintKeysAndValues( Hashtable myHT )
   {
      Console.WriteLine("\t-KEY-\t-VALUE-");
      foreach (DictionaryEntry de in myHT)
         Console.WriteLine($"\t{de.Key}:\t{de.Value}");
      Console.WriteLine();
   }
}
/*
This code produces the following output.

The Hashtable contains the following:
        -KEY-   -VALUE-
        two:    quick
        three:  brown
        four:   fox
        one:    The
*/
Imports System.Collections

Public Class SamplesHashtable

    Public Shared Sub Main()

        ' Creates and initializes a new Hashtable.
        Dim myHT As New Hashtable()
        myHT.Add("one", "The")
        myHT.Add("two", "quick")
        myHT.Add("three", "brown")
        myHT.Add("four", "fox")

        ' Displays the Hashtable.
        Console.WriteLine("The Hashtable contains the following:")
        PrintKeysAndValues(myHT)

    End Sub

    Public Shared Sub PrintKeysAndValues(myHT As Hashtable)
        Console.WriteLine(vbTab + "-KEY-" + vbTab + "-VALUE-")
        For Each de As DictionaryEntry In myHT
            Console.WriteLine(vbTab + "{0}:" + vbTab + "{1}", de.Key, de.Value)
        Next
        Console.WriteLine()
    End Sub

End Class


' This code produces the following output.
' 
' The Hashtable contains the following:
'         -KEY-   -VALUE-
'         two:    quick
'         one:    The
'         three:  brown
'         four:   fox
' 

Comentarios

Una clave no puede ser null , pero un valor puede ser.A key cannot be null, but a value can be.

Un objeto que no tiene ninguna correlación entre su estado y su valor de código hash no debe usarse normalmente como clave.An object that has no correlation between its state and its hash code value should typically not be used as the key. Por ejemplo, los objetos de cadena son mejores que los objetos StringBuilder para su uso como claves.For example, String objects are better than StringBuilder objects for use as keys.

También puede usar la Item[] propiedad para agregar nuevos elementos estableciendo el valor de una clave que no existe en Hashtable ; por ejemplo, myCollection["myNonexistentKey"] = myValue .You can also use the Item[] property to add new elements by setting the value of a key that does not exist in the Hashtable; for example, myCollection["myNonexistentKey"] = myValue. Sin embargo, si la clave especificada ya existe en Hashtable , al establecer la Item[] propiedad se sobrescribe el valor anterior.However, if the specified key already exists in the Hashtable, setting the Item[] property overwrites the old value. En cambio, el Add método no modifica los elementos existentes.In contrast, the Add method does not modify existing elements.

Si Count es menor que la capacidad de Hashtable , este método es una O(1) operación.If Count is less than the capacity of the Hashtable, this method is an O(1) operation. Si es necesario aumentar la capacidad para alojar el nuevo elemento, este método se convierte en una O(n) operación, donde n es Count .If the capacity needs to be increased to accommodate the new element, this method becomes an O(n) operation, where n is Count.

Se aplica a

Consulte también