KeyedCollection<TKey,TItem> Constructores
Definición
Importante
Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.
Inicializa una nueva instancia de la clase KeyedCollection<TKey,TItem>.
Sobrecargas
| KeyedCollection<TKey,TItem>() |
Inicializa una nueva instancia de la clase KeyedCollection<TKey,TItem> que utiliza el comparador de igualdad predeterminado. |
| KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>) |
Inicializa una nueva instancia de la clase KeyedCollection<TKey,TItem> que utiliza el comparador de igualdad especificado. |
| KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) |
Inicializa una nueva instancia de la clase KeyedCollection<TKey,TItem> que utiliza el comparador de igualdad especificado y crea un diccionario de búsqueda cuando se supera el umbral especificado. |
KeyedCollection<TKey,TItem>()
- Source:
- KeyedCollection.cs
- Source:
- KeyedCollection.cs
- Source:
- KeyedCollection.cs
Inicializa una nueva instancia de la clase KeyedCollection<TKey,TItem> que utiliza el comparador de igualdad predeterminado.
protected:
KeyedCollection();protected KeyedCollection ();Protected Sub New ()Ejemplos
En este ejemplo de código se muestra el código mínimo necesario para derivar una clase de colección de KeyedCollection<TKey,TItem>: invalidar el GetKeyForItem método y proporcionar un constructor público que delega en un constructor de clase base. En el ejemplo de código también se muestran muchas de las propiedades y métodos heredados de KeyedCollection<TKey,TItem> las clases y Collection<T> .
La SimpleOrder clase es una lista de solicitudes muy sencilla que contiene OrderItem objetos, cada uno de los cuales representa un elemento de línea en el orden. La clave de OrderItem es inmutable, una consideración importante para las clases que derivan de KeyedCollection<TKey,TItem>. Para obtener un ejemplo de código que usa claves mutables, vea ChangeItemKey.
using namespace System;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;
// This class represents a simple line item in an order. All the
// values are immutable except quantity.
//
public ref class OrderItem
{
private:
int _quantity;
public:
initonly int PartNumber;
initonly String^ Description;
initonly double UnitPrice;
OrderItem(int partNumber, String^ description,
int quantity, double unitPrice)
{
this->PartNumber = partNumber;
this->Description = description;
this->Quantity = quantity;
this->UnitPrice = unitPrice;
}
property int Quantity
{
int get() { return _quantity; }
void set(int value)
{
if (value < 0)
throw gcnew ArgumentException("Quantity cannot be negative.");
_quantity = value;
}
}
virtual String^ ToString() override
{
return String::Format(
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
PartNumber, _quantity, Description, UnitPrice,
UnitPrice * _quantity);
}
};
// This class represents a very simple keyed list of OrderItems,
// inheriting most of its behavior from the KeyedCollection and
// Collection classes. The immediate base class is the constructed
// type KeyedCollection<int, OrderItem>. When you inherit
// from KeyedCollection, the second generic type argument is the
// type that you want to store in the collection -- in this case
// OrderItem. The first type argument is the type that you want
// to use as a key. Its values must be calculated from OrderItem;
// in this case it is the int field PartNumber, so SimpleOrder
// inherits KeyedCollection<int, OrderItem>.
//
public ref class SimpleOrder : KeyedCollection<int, OrderItem^>
{
// The parameterless constructor of the base class creates a
// KeyedCollection with an internal dictionary. For this code
// example, no other constructors are exposed.
//
public:
SimpleOrder() {}
// This is the only method that absolutely must be overridden,
// because without it the KeyedCollection cannot extract the
// keys from the items. The input parameter type is the
// second generic type argument, in this case OrderItem, and
// the return value type is the first generic type argument,
// in this case int.
//
protected:
virtual int GetKeyForItem(OrderItem^ item) override
{
// In this example, the key is the part number.
return item->PartNumber;
}
};
public ref class Demo
{
public:
static void Main()
{
SimpleOrder^ weekly = gcnew SimpleOrder();
// The Add method, inherited from Collection, takes OrderItem.
//
weekly->Add(gcnew OrderItem(110072674, "Widget", 400, 45.17));
weekly->Add(gcnew OrderItem(110072675, "Sprocket", 27, 5.3));
weekly->Add(gcnew OrderItem(101030411, "Motor", 10, 237.5));
weekly->Add(gcnew OrderItem(110072684, "Gear", 175, 5.17));
Display(weekly);
// The Contains method of KeyedCollection takes the key,
// type, in this case int.
//
Console::WriteLine("\nContains(101030411): {0}",
weekly->Contains(101030411));
// The default Item property of KeyedCollection takes a key.
//
Console::WriteLine("\nweekly(101030411)->Description: {0}",
weekly[101030411]->Description);
// The Remove method of KeyedCollection takes a key.
//
Console::WriteLine("\nRemove(101030411)");
weekly->Remove(101030411);
Display(weekly);
// The Insert method, inherited from Collection, takes an
// index and an OrderItem.
//
Console::WriteLine("\nInsert(2, New OrderItem(...))");
weekly->Insert(2, gcnew OrderItem(111033401, "Nut", 10, .5));
Display(weekly);
// The default Item property is overloaded. One overload comes
// from KeyedCollection<int, OrderItem>; that overload
// is read-only, and takes Integer because it retrieves by key.
// The other overload comes from Collection<OrderItem>, the
// base class of KeyedCollection<int, OrderItem>; it
// retrieves by index, so it also takes an Integer. The compiler
// uses the most-derived overload, from KeyedCollection, so the
// only way to access SimpleOrder by index is to cast it to
// Collection<OrderItem>. Otherwise the index is interpreted
// as a key, and KeyNotFoundException is thrown.
//
Collection<OrderItem^>^ coweekly = weekly;
Console::WriteLine("\ncoweekly[2].Description: {0}",
coweekly[2]->Description);
Console::WriteLine("\ncoweekly[2] = gcnew OrderItem(...)");
coweekly[2] = gcnew OrderItem(127700026, "Crank", 27, 5.98);
OrderItem^ temp = coweekly[2];
// The IndexOf method inherited from Collection<OrderItem>
// takes an OrderItem instead of a key
//
Console::WriteLine("\nIndexOf(temp): {0}", weekly->IndexOf(temp));
// The inherited Remove method also takes an OrderItem.
//
Console::WriteLine("\nRemove(temp)");
weekly->Remove(temp);
Display(weekly);
Console::WriteLine("\nRemoveAt(0)");
weekly->RemoveAt(0);
Display(weekly);
}
private:
static void Display(SimpleOrder^ order)
{
Console::WriteLine();
for each( OrderItem^ item in order )
{
Console::WriteLine(item);
}
}
};
void main()
{
Demo::Main();
}
/* This code example produces the following output:
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
101030411 10 Motor at 237.50 = 2,375.00
110072684 175 Gear at 5.17 = 904.75
Contains(101030411): True
weekly(101030411)->Description: Motor
Remove(101030411)
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
110072684 175 Gear at 5.17 = 904.75
Insert(2, New OrderItem(...))
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
111033401 10 Nut at .50 = 5.00
110072684 175 Gear at 5.17 = 904.75
coweekly(2)->Description: Nut
coweekly[2] = gcnew OrderItem(...)
IndexOf(temp): 2
Remove(temp)
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
110072684 175 Gear at 5.17 = 904.75
RemoveAt(0)
110072675 27 Sprocket at 5.30 = 143.10
110072684 175 Gear at 5.17 = 904.75
*/
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
// This class represents a very simple keyed list of OrderItems,
// inheriting most of its behavior from the KeyedCollection and
// Collection classes. The immediate base class is the constructed
// type KeyedCollection<int, OrderItem>. When you inherit
// from KeyedCollection, the second generic type argument is the
// type that you want to store in the collection -- in this case
// OrderItem. The first type argument is the type that you want
// to use as a key. Its values must be calculated from OrderItem;
// in this case it is the int field PartNumber, so SimpleOrder
// inherits KeyedCollection<int, OrderItem>.
//
public class SimpleOrder : KeyedCollection<int, OrderItem>
{
// This is the only method that absolutely must be overridden,
// because without it the KeyedCollection cannot extract the
// keys from the items. The input parameter type is the
// second generic type argument, in this case OrderItem, and
// the return value type is the first generic type argument,
// in this case int.
//
protected override int GetKeyForItem(OrderItem item)
{
// In this example, the key is the part number.
return item.PartNumber;
}
}
public class Demo
{
public static void Main()
{
SimpleOrder weekly = new SimpleOrder();
// The Add method, inherited from Collection, takes OrderItem.
//
weekly.Add(new OrderItem(110072674, "Widget", 400, 45.17));
weekly.Add(new OrderItem(110072675, "Sprocket", 27, 5.3));
weekly.Add(new OrderItem(101030411, "Motor", 10, 237.5));
weekly.Add(new OrderItem(110072684, "Gear", 175, 5.17));
Display(weekly);
// The Contains method of KeyedCollection takes the key,
// type, in this case int.
//
Console.WriteLine("\nContains(101030411): {0}",
weekly.Contains(101030411));
// The default Item property of KeyedCollection takes a key.
//
Console.WriteLine("\nweekly[101030411].Description: {0}",
weekly[101030411].Description);
// The Remove method of KeyedCollection takes a key.
//
Console.WriteLine("\nRemove(101030411)");
weekly.Remove(101030411);
Display(weekly);
// The Insert method, inherited from Collection, takes an
// index and an OrderItem.
//
Console.WriteLine("\nInsert(2, New OrderItem(...))");
weekly.Insert(2, new OrderItem(111033401, "Nut", 10, .5));
Display(weekly);
// The default Item property is overloaded. One overload comes
// from KeyedCollection<int, OrderItem>; that overload
// is read-only, and takes Integer because it retrieves by key.
// The other overload comes from Collection<OrderItem>, the
// base class of KeyedCollection<int, OrderItem>; it
// retrieves by index, so it also takes an Integer. The compiler
// uses the most-derived overload, from KeyedCollection, so the
// only way to access SimpleOrder by index is to cast it to
// Collection<OrderItem>. Otherwise the index is interpreted
// as a key, and KeyNotFoundException is thrown.
//
Collection<OrderItem> coweekly = weekly;
Console.WriteLine("\ncoweekly[2].Description: {0}",
coweekly[2].Description);
Console.WriteLine("\ncoweekly[2] = new OrderItem(...)");
coweekly[2] = new OrderItem(127700026, "Crank", 27, 5.98);
OrderItem temp = coweekly[2];
// The IndexOf method inherited from Collection<OrderItem>
// takes an OrderItem instead of a key
//
Console.WriteLine("\nIndexOf(temp): {0}", weekly.IndexOf(temp));
// The inherited Remove method also takes an OrderItem.
//
Console.WriteLine("\nRemove(temp)");
weekly.Remove(temp);
Display(weekly);
Console.WriteLine("\nRemoveAt(0)");
weekly.RemoveAt(0);
Display(weekly);
}
private static void Display(SimpleOrder order)
{
Console.WriteLine();
foreach( OrderItem item in order )
{
Console.WriteLine(item);
}
}
}
// This class represents a simple line item in an order. All the
// values are immutable except quantity.
//
public class OrderItem
{
public readonly int PartNumber;
public readonly string Description;
public readonly double UnitPrice;
private int _quantity = 0;
public OrderItem(int partNumber, string description,
int quantity, double unitPrice)
{
this.PartNumber = partNumber;
this.Description = description;
this.Quantity = quantity;
this.UnitPrice = unitPrice;
}
public int Quantity
{
get { return _quantity; }
set
{
if (value<0)
throw new ArgumentException("Quantity cannot be negative.");
_quantity = value;
}
}
public override string ToString()
{
return String.Format(
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
PartNumber, _quantity, Description, UnitPrice,
UnitPrice * _quantity);
}
}
/* This code example produces the following output:
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
101030411 10 Motor at 237.50 = 2,375.00
110072684 175 Gear at 5.17 = 904.75
Contains(101030411): True
weekly[101030411].Description: Motor
Remove(101030411)
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
110072684 175 Gear at 5.17 = 904.75
Insert(2, New OrderItem(...))
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
111033401 10 Nut at .50 = 5.00
110072684 175 Gear at 5.17 = 904.75
coweekly[2].Description: Nut
coweekly[2] = new OrderItem(...)
IndexOf(temp): 2
Remove(temp)
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
110072684 175 Gear at 5.17 = 904.75
RemoveAt(0)
110072675 27 Sprocket at 5.30 = 143.10
110072684 175 Gear at 5.17 = 904.75
*/
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
' This class represents a very simple keyed list of OrderItems,
' inheriting most of its behavior from the KeyedCollection and
' Collection classes. The immediate base class is the constructed
' type KeyedCollection(Of Integer, OrderItem). When you inherit
' from KeyedCollection, the second generic type argument is the
' type that you want to store in the collection -- in this case
' OrderItem. The first generic argument is the type that you want
' to use as a key. Its values must be calculated from OrderItem;
' in this case it is the Integer field PartNumber, so SimpleOrder
' inherits KeyedCollection(Of Integer, OrderItem).
'
Public Class SimpleOrder
Inherits KeyedCollection(Of Integer, OrderItem)
' This is the only method that absolutely must be overridden,
' because without it the KeyedCollection cannot extract the
' keys from the items. The input parameter type is the
' second generic type argument, in this case OrderItem, and
' the return value type is the first generic type argument,
' in this case Integer.
'
Protected Overrides Function GetKeyForItem( _
ByVal item As OrderItem) As Integer
' In this example, the key is the part number.
Return item.PartNumber
End Function
End Class
Public Class Demo
Public Shared Sub Main()
Dim weekly As New SimpleOrder()
' The Add method, inherited from Collection, takes OrderItem.
'
weekly.Add(New OrderItem(110072674, "Widget", 400, 45.17))
weekly.Add(New OrderItem(110072675, "Sprocket", 27, 5.3))
weekly.Add(New OrderItem(101030411, "Motor", 10, 237.5))
weekly.Add(New OrderItem(110072684, "Gear", 175, 5.17))
Display(weekly)
' The Contains method of KeyedCollection takes TKey.
'
Console.WriteLine(vbLf & "Contains(101030411): {0}", _
weekly.Contains(101030411))
' The default Item property of KeyedCollection takes the key
' type, Integer.
'
Console.WriteLine(vbLf & "weekly(101030411).Description: {0}", _
weekly(101030411).Description)
' The Remove method of KeyedCollection takes a key.
'
Console.WriteLine(vbLf & "Remove(101030411)")
weekly.Remove(101030411)
Display(weekly)
' The Insert method, inherited from Collection, takes an
' index and an OrderItem.
'
Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
weekly.Insert(2, New OrderItem(111033401, "Nut", 10, .5))
Display(weekly)
' The default Item property is overloaded. One overload comes
' from KeyedCollection(Of Integer, OrderItem); that overload
' is read-only, and takes Integer because it retrieves by key.
' The other overload comes from Collection(Of OrderItem), the
' base class of KeyedCollection(Of Integer, OrderItem); it
' retrieves by index, so it also takes an Integer. The compiler
' uses the most-derived overload, from KeyedCollection, so the
' only way to access SimpleOrder by index is to cast it to
' Collection(Of OrderItem). Otherwise the index is interpreted
' as a key, and KeyNotFoundException is thrown.
'
Dim coweekly As Collection(Of OrderItem) = weekly
Console.WriteLine(vbLf & "coweekly(2).Description: {0}", _
coweekly(2).Description)
Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
coweekly(2) = New OrderItem(127700026, "Crank", 27, 5.98)
Dim temp As OrderItem = coweekly(2)
' The IndexOf method, inherited from Collection(Of OrderItem),
' takes an OrderItem instead of a key.
'
Console.WriteLine(vbLf & "IndexOf(temp): {0}", _
weekly.IndexOf(temp))
' The inherited Remove method also takes an OrderItem.
'
Console.WriteLine(vbLf & "Remove(temp)")
weekly.Remove(temp)
Display(weekly)
Console.WriteLine(vbLf & "RemoveAt(0)")
weekly.RemoveAt(0)
Display(weekly)
End Sub
Private Shared Sub Display(ByVal order As SimpleOrder)
Console.WriteLine()
For Each item As OrderItem In order
Console.WriteLine(item)
Next item
End Sub
End Class
' This class represents a simple line item in an order. All the
' values are immutable except quantity.
'
Public Class OrderItem
Public ReadOnly PartNumber As Integer
Public ReadOnly Description As String
Public ReadOnly UnitPrice As Double
Private _quantity As Integer = 0
Public Sub New(ByVal partNumber As Integer, _
ByVal description As String, _
ByVal quantity As Integer, _
ByVal unitPrice As Double)
Me.PartNumber = partNumber
Me.Description = description
Me.Quantity = quantity
Me.UnitPrice = unitPrice
End Sub
Public Property Quantity() As Integer
Get
Return _quantity
End Get
Set
If value < 0 Then
Throw New ArgumentException("Quantity cannot be negative.")
End If
_quantity = value
End Set
End Property
Public Overrides Function ToString() As String
Return String.Format( _
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}", _
PartNumber, _quantity, Description, UnitPrice, _
UnitPrice * _quantity)
End Function
End Class
' This code example produces the following output:
'
'110072674 400 Widget at 45.17 = 18,068.00
'110072675 27 Sprocket at 5.30 = 143.10
'101030411 10 Motor at 237.50 = 2,375.00
'110072684 175 Gear at 5.17 = 904.75
'
'Contains(101030411): True
'
'weekly(101030411).Description: Motor
'
'Remove(101030411)
'
'110072674 400 Widget at 45.17 = 18,068.00
'110072675 27 Sprocket at 5.30 = 143.10
'110072684 175 Gear at 5.17 = 904.75
'
'Insert(2, New OrderItem(...))
'
'110072674 400 Widget at 45.17 = 18,068.00
'110072675 27 Sprocket at 5.30 = 143.10
'111033401 10 Nut at .50 = 5.00
'110072684 175 Gear at 5.17 = 904.75
'
'coweekly(2).Description: Nut
'
'coweekly(2) = New OrderItem(...)
'
'IndexOf(temp): 2
'
'Remove(temp)
'
'110072674 400 Widget at 45.17 = 18,068.00
'110072675 27 Sprocket at 5.30 = 143.10
'110072684 175 Gear at 5.17 = 904.75
'
'RemoveAt(0)
'
'110072675 27 Sprocket at 5.30 = 143.10
'110072684 175 Gear at 5.17 = 904.75
Comentarios
Un KeyedCollection<TKey,TItem> objeto creado con este constructor usa el comparador de igualdad genérico predeterminado para el tipo de la clave, obtenido de EqualityComparer<T>.Default. Para especificar un comparador de igualdad genérico diferente, use el KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>) constructor o el KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor .
De forma predeterminada, KeyedCollection<TKey,TItem> incluye un diccionario de búsqueda que se crea cuando se agrega el primer elemento. Cuando se agrega un elemento a KeyedCollection<TKey,TItem>, la clave del elemento se extrae una vez y se guarda en el diccionario de búsqueda para búsquedas más rápidas. Este comportamiento se puede invalidar mediante el KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor y especificando un umbral de creación del diccionario.
Nota:
Dado que la KeyedCollection<TKey,TItem> clase es abstracta (MustInherit en Visual Basic), debe derivar de ella para poder usarla. En el constructor del tipo derivado, llame al constructor adecuado KeyedCollection<TKey,TItem> . No es necesario exponer funcionalidad como el comparador de igualdad o el umbral de creación del diccionario en los constructores.
Este constructor es una operación O(1).
Consulte también
Se aplica a
KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>)
- Source:
- KeyedCollection.cs
- Source:
- KeyedCollection.cs
- Source:
- KeyedCollection.cs
Inicializa una nueva instancia de la clase KeyedCollection<TKey,TItem> que utiliza el comparador de igualdad especificado.
protected:
KeyedCollection(System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);protected KeyedCollection (System.Collections.Generic.IEqualityComparer<TKey> comparer);protected KeyedCollection (System.Collections.Generic.IEqualityComparer<TKey>? comparer);new System.Collections.ObjectModel.KeyedCollection<'Key, 'Item> : System.Collections.Generic.IEqualityComparer<'Key> -> System.Collections.ObjectModel.KeyedCollection<'Key, 'Item>Protected Sub New (comparer As IEqualityComparer(Of TKey))Parámetros
- comparer
- IEqualityComparer<TKey>
Implementación de la interfaz genérica IEqualityComparer<T> que se va a usar al comparar claves, o null para usar el comparador de igualdad predeterminado para el tipo de clave, que se obtiene de Default.
Comentarios
De forma predeterminada, KeyedCollection<TKey,TItem> incluye un diccionario de búsqueda que se crea cuando se agrega el primer elemento. Cuando se agrega un elemento a KeyedCollection<TKey,TItem>, la clave del elemento se extrae una vez y se guarda en el diccionario de búsqueda para búsquedas más rápidas. Este comportamiento se puede invalidar mediante el KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor y especificando un umbral de creación del diccionario.
Nota
Dado que la KeyedCollection<TKey,TItem> clase es abstracta (MustInherit en Visual Basic), debe derivar de ella para poder usarla. En el constructor del tipo derivado, llame al constructor adecuado KeyedCollection<TKey,TItem> . No es necesario exponer funcionalidad como el comparador de igualdad o el umbral de creación del diccionario en los constructores.
Este constructor es una operación O(1).
Consulte también
Se aplica a
KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32)
- Source:
- KeyedCollection.cs
- Source:
- KeyedCollection.cs
- Source:
- KeyedCollection.cs
Inicializa una nueva instancia de la clase KeyedCollection<TKey,TItem> que utiliza el comparador de igualdad especificado y crea un diccionario de búsqueda cuando se supera el umbral especificado.
protected:
KeyedCollection(System::Collections::Generic::IEqualityComparer<TKey> ^ comparer, int dictionaryCreationThreshold);protected KeyedCollection (System.Collections.Generic.IEqualityComparer<TKey> comparer, int dictionaryCreationThreshold);protected KeyedCollection (System.Collections.Generic.IEqualityComparer<TKey>? comparer, int dictionaryCreationThreshold);new System.Collections.ObjectModel.KeyedCollection<'Key, 'Item> : System.Collections.Generic.IEqualityComparer<'Key> * int -> System.Collections.ObjectModel.KeyedCollection<'Key, 'Item>Protected Sub New (comparer As IEqualityComparer(Of TKey), dictionaryCreationThreshold As Integer)Parámetros
- comparer
- IEqualityComparer<TKey>
Implementación de la interfaz genérica IEqualityComparer<T> que se va a usar al comparar claves, o null para usar el comparador de igualdad predeterminado para el tipo de clave, que se obtiene de Default.
- dictionaryCreationThreshold
- Int32
Número de elementos que puede contener la colección sin crear un diccionario de búsqueda (0 crea el diccionario de búsqueda al agregar el primer elemento), o -1 para especificar que nunca se crea un diccionario de búsqueda.
Excepciones
dictionaryCreationThreshold es menor que 1.
Ejemplos
En el ejemplo de código siguiente se muestra cómo invalidar los métodos protegidos InsertItem, ClearItemsRemoveItem, , y SetItem para proporcionar un comportamiento personalizado para los Addmétodos , Removey Clear para establecer la propiedad predeterminada Item[] (el indexador en C#). El comportamiento personalizado proporcionado en este ejemplo es un evento de notificación denominado Changed, que se genera al final de cada uno de los métodos invalidados.
En el ejemplo de código se usa el KeyedCollection<TKey,TItem>(IEqualityComparer<TKey>, Int32) constructor con un umbral de 0, por lo que el diccionario interno se crea la primera vez que se agrega un objeto a la colección.
El ejemplo de código crea la SimpleOrder clase , que deriva de KeyedCollection<TKey,TItem> y representa un formulario de orden simple. El formulario de pedido contiene OrderItem objetos que representan elementos ordenados. El ejemplo de código también crea una SimpleOrderChangedEventArgs clase para contener la información del evento y una enumeración para identificar el tipo de cambio.
En el ejemplo de código se muestra el comportamiento personalizado llamando a las propiedades y métodos de la clase derivada, en el Main método de la Demo clase .
En este ejemplo de código se usan objetos con claves inmutables. Para obtener un ejemplo de código que usa claves mutables, vea ChangeItemKey.
using namespace System;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;
public enum class ChangeTypes
{
Added,
Removed,
Replaced,
Cleared
};
ref class SimpleOrderChangedEventArgs;
// This class represents a simple line item in an order. All the
// values are immutable except quantity.
//
public ref class OrderItem
{
private:
int _quantity;
public:
initonly int PartNumber;
initonly String^ Description;
initonly double UnitPrice;
OrderItem(int partNumber, String^ description, int quantity,
double unitPrice)
{
this->PartNumber = partNumber;
this->Description = description;
this->Quantity = quantity;
this->UnitPrice = unitPrice;
};
property int Quantity
{
int get() { return _quantity; };
void set(int value)
{
if (value < 0)
throw gcnew ArgumentException("Quantity cannot be negative.");
_quantity = value;
};
};
virtual String^ ToString() override
{
return String::Format(
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
PartNumber, _quantity, Description, UnitPrice,
UnitPrice * _quantity);
};
};
// Event argument for the Changed event.
//
public ref class SimpleOrderChangedEventArgs : EventArgs
{
public:
OrderItem^ ChangedItem;
initonly ChangeTypes ChangeType;
OrderItem^ ReplacedWith;
SimpleOrderChangedEventArgs(ChangeTypes change,
OrderItem^ item, OrderItem^ replacement)
{
this->ChangeType = change;
this->ChangedItem = item;
this->ReplacedWith = replacement;
}
};
// This class derives from KeyedCollection and shows how to override
// the protected ClearItems, InsertItem, RemoveItem, and SetItem
// methods in order to change the behavior of the default Item
// property and the Add, Clear, Insert, and Remove methods. The
// class implements a Changed event, which is raised by all the
// protected methods.
//
// SimpleOrder is a collection of OrderItem objects, and its key
// is the PartNumber field of OrderItem-> PartNumber is an Integer,
// so SimpleOrder inherits KeyedCollection<int, OrderItem>.
// (Note that the key of OrderItem cannot be changed; if it could
// be changed, SimpleOrder would have to override ChangeItemKey.)
//
public ref class SimpleOrder : KeyedCollection<int, OrderItem^>
{
public:
event EventHandler<SimpleOrderChangedEventArgs^>^ Changed;
// This parameterless constructor calls the base class constructor
// that specifies a dictionary threshold of 0, so that the internal
// dictionary is created as soon as an item is added to the
// collection.
//
SimpleOrder() : KeyedCollection<int, OrderItem^>(nullptr, 0) {};
// This is the only method that absolutely must be overridden,
// because without it the KeyedCollection cannot extract the
// keys from the items.
//
protected:
virtual int GetKeyForItem(OrderItem^ item) override
{
// In this example, the key is the part number.
return item->PartNumber;
}
virtual void InsertItem(int index, OrderItem^ newItem) override
{
__super::InsertItem(index, newItem);
Changed(this, gcnew SimpleOrderChangedEventArgs(
ChangeTypes::Added, newItem, nullptr));
}
virtual void SetItem(int index, OrderItem^ newItem) override
{
OrderItem^ replaced = this->Items[index];
__super::SetItem(index, newItem);
Changed(this, gcnew SimpleOrderChangedEventArgs(
ChangeTypes::Replaced, replaced, newItem));
}
virtual void RemoveItem(int index) override
{
OrderItem^ removedItem = Items[index];
__super::RemoveItem(index);
Changed(this, gcnew SimpleOrderChangedEventArgs(
ChangeTypes::Removed, removedItem, nullptr));
}
virtual void ClearItems() override
{
__super::ClearItems();
Changed(this, gcnew SimpleOrderChangedEventArgs(
ChangeTypes::Cleared, nullptr, nullptr));
}
// This method uses the internal reference to the dictionary
// to test fo
public:
void AddOrMerge(OrderItem^ newItem)
{
int key = this->GetKeyForItem(newItem);
OrderItem^ existingItem = nullptr;
// The dictionary is not created until the first item is
// added, so it is necessary to test for null. Using
// AndAlso ensures that TryGetValue is not called if the
// dictionary does not exist.
//
if (this->Dictionary != nullptr &&
this->Dictionary->TryGetValue(key, existingItem))
{
existingItem->Quantity += newItem->Quantity;
}
else
{
this->Add(newItem);
}
}
};
public ref class Demo
{
public:
static void Main()
{
SimpleOrder^ weekly = gcnew SimpleOrder();
weekly->Changed += gcnew
EventHandler<SimpleOrderChangedEventArgs^>(ChangedHandler);
// The Add method, inherited from Collection, takes OrderItem->
//
weekly->Add(gcnew OrderItem(110072674, "Widget", 400, 45.17));
weekly->Add(gcnew OrderItem(110072675, "Sprocket", 27, 5.3));
weekly->Add(gcnew OrderItem(101030411, "Motor", 10, 237.5));
weekly->Add(gcnew OrderItem(110072684, "Gear", 175, 5.17));
Display(weekly);
// The Contains method of KeyedCollection takes TKey.
//
Console::WriteLine("\nContains(101030411): {0}",
weekly->Contains(101030411));
// The default Item property of KeyedCollection takes the key
// type, Integer. The property is read-only.
//
Console::WriteLine("\nweekly[101030411]->Description: {0}",
weekly[101030411]->Description);
// The Remove method of KeyedCollection takes a key.
//
Console::WriteLine("\nRemove(101030411)");
weekly->Remove(101030411);
// The Insert method, inherited from Collection, takes an
// index and an OrderItem.
//
Console::WriteLine("\nInsert(2, gcnew OrderItem(...))");
weekly->Insert(2, gcnew OrderItem(111033401, "Nut", 10, .5));
// The default Item property is overloaded. One overload comes
// from KeyedCollection<int, OrderItem>; that overload
// is read-only, and takes Integer because it retrieves by key.
// The other overload comes from Collection<OrderItem>, the
// base class of KeyedCollection<int, OrderItem>; it
// retrieves by index, so it also takes an Integer. The compiler
// uses the most-derived overload, from KeyedCollection, so the
// only way to access SimpleOrder by index is to cast it to
// Collection<OrderItem>. Otherwise the index is interpreted
// as a key, and KeyNotFoundException is thrown.
//
Collection<OrderItem^>^ coweekly = weekly;
Console::WriteLine("\ncoweekly[2].Description: {0}",
coweekly[2]->Description);
Console::WriteLine("\ncoweekly[2] = gcnew OrderItem(...)");
coweekly[2] = gcnew OrderItem(127700026, "Crank", 27, 5.98);
OrderItem^ temp = coweekly[2];
// The IndexOf method, inherited from Collection<OrderItem>,
// takes an OrderItem instead of a key.
//
Console::WriteLine("\nIndexOf(temp): {0}", weekly->IndexOf(temp));
// The inherited Remove method also takes an OrderItem->
//
Console::WriteLine("\nRemove(temp)");
weekly->Remove(temp);
Console::WriteLine("\nRemoveAt(0)");
weekly->RemoveAt(0);
weekly->AddOrMerge(gcnew OrderItem(110072684, "Gear", 1000, 5.17));
Display(weekly);
Console::WriteLine();
weekly->Clear();
}
private:
static void Display(SimpleOrder^ order)
{
Console::WriteLine();
for each( OrderItem^ item in order )
{
Console::WriteLine(item);
}
}
static void ChangedHandler(Object^ source,
SimpleOrderChangedEventArgs^ e)
{
OrderItem^ item = e->ChangedItem;
if (e->ChangeType == ChangeTypes::Replaced)
{
OrderItem^ replacement = e->ReplacedWith;
Console::WriteLine("{0} (quantity {1}) was replaced " +
"by {2}, (quantity {3}).", item->Description,
item->Quantity, replacement->Description,
replacement->Quantity);
}
else if(e->ChangeType == ChangeTypes::Cleared)
{
Console::WriteLine("The order list was cleared.");
}
else
{
Console::WriteLine("{0} (quantity {1}) was {2}.",
item->Description, item->Quantity, e->ChangeType);
}
}
};
void main()
{
Demo::Main();
}
/* This code example produces the following output:
Widget (quantity 400) was Added.
Sprocket (quantity 27) was Added.
Motor (quantity 10) was Added.
Gear (quantity 175) was Added.
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
101030411 10 Motor at 237.50 = 2,375.00
110072684 175 Gear at 5.17 = 904.75
Contains(101030411): True
weekly[101030411]->Description: Motor
Remove(101030411)
Motor (quantity 10) was Removed.
Insert(2, gcnew OrderItem(...))
Nut (quantity 10) was Added.
coweekly[2].Description: Nut
coweekly[2] = gcnew OrderItem(...)
Nut (quantity 10) was replaced by Crank, (quantity 27).
IndexOf(temp): 2
Remove(temp)
Crank (quantity 27) was Removed.
RemoveAt(0)
Widget (quantity 400) was Removed.
110072675 27 Sprocket at 5.30 = 143.10
110072684 1175 Gear at 5.17 = 6,074.75
The order list was cleared.
*/
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
// This class derives from KeyedCollection and shows how to override
// the protected ClearItems, InsertItem, RemoveItem, and SetItem
// methods in order to change the behavior of the default Item
// property and the Add, Clear, Insert, and Remove methods. The
// class implements a Changed event, which is raised by all the
// protected methods.
//
// SimpleOrder is a collection of OrderItem objects, and its key
// is the PartNumber field of OrderItem. PartNumber is an Integer,
// so SimpleOrder inherits KeyedCollection<int, OrderItem>.
// (Note that the key of OrderItem cannot be changed; if it could
// be changed, SimpleOrder would have to override ChangeItemKey.)
//
public class SimpleOrder : KeyedCollection<int, OrderItem>
{
public event EventHandler<SimpleOrderChangedEventArgs> Changed;
// This parameterless constructor calls the base class constructor
// that specifies a dictionary threshold of 0, so that the internal
// dictionary is created as soon as an item is added to the
// collection.
//
public SimpleOrder() : base(null, 0) {}
// This is the only method that absolutely must be overridden,
// because without it the KeyedCollection cannot extract the
// keys from the items.
//
protected override int GetKeyForItem(OrderItem item)
{
// In this example, the key is the part number.
return item.PartNumber;
}
protected override void InsertItem(int index, OrderItem newItem)
{
base.InsertItem(index, newItem);
EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
if (temp != null)
{
temp(this, new SimpleOrderChangedEventArgs(
ChangeType.Added, newItem, null));
}
}
protected override void SetItem(int index, OrderItem newItem)
{
OrderItem replaced = Items[index];
base.SetItem(index, newItem);
EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
if (temp != null)
{
temp(this, new SimpleOrderChangedEventArgs(
ChangeType.Replaced, replaced, newItem));
}
}
protected override void RemoveItem(int index)
{
OrderItem removedItem = Items[index];
base.RemoveItem(index);
EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
if (temp != null)
{
temp(this, new SimpleOrderChangedEventArgs(
ChangeType.Removed, removedItem, null));
}
}
protected override void ClearItems()
{
base.ClearItems();
EventHandler<SimpleOrderChangedEventArgs> temp = Changed;
if (temp != null)
{
temp(this, new SimpleOrderChangedEventArgs(
ChangeType.Cleared, null, null));
}
}
}
// Event argument for the Changed event.
//
public class SimpleOrderChangedEventArgs : EventArgs
{
private OrderItem _changedItem;
private ChangeType _changeType;
private OrderItem _replacedWith;
public OrderItem ChangedItem { get { return _changedItem; }}
public ChangeType ChangeType { get { return _changeType; }}
public OrderItem ReplacedWith { get { return _replacedWith; }}
public SimpleOrderChangedEventArgs(ChangeType change,
OrderItem item, OrderItem replacement)
{
_changeType = change;
_changedItem = item;
_replacedWith = replacement;
}
}
public enum ChangeType
{
Added,
Removed,
Replaced,
Cleared
};
public class Demo
{
public static void Main()
{
SimpleOrder weekly = new SimpleOrder();
weekly.Changed += new
EventHandler<SimpleOrderChangedEventArgs>(ChangedHandler);
// The Add method, inherited from Collection, takes OrderItem.
//
weekly.Add(new OrderItem(110072674, "Widget", 400, 45.17));
weekly.Add(new OrderItem(110072675, "Sprocket", 27, 5.3));
weekly.Add(new OrderItem(101030411, "Motor", 10, 237.5));
weekly.Add(new OrderItem(110072684, "Gear", 175, 5.17));
Display(weekly);
// The Contains method of KeyedCollection takes TKey.
//
Console.WriteLine("\nContains(101030411): {0}",
weekly.Contains(101030411));
// The default Item property of KeyedCollection takes the key
// type, Integer. The property is read-only.
//
Console.WriteLine("\nweekly[101030411].Description: {0}",
weekly[101030411].Description);
// The Remove method of KeyedCollection takes a key.
//
Console.WriteLine("\nRemove(101030411)");
weekly.Remove(101030411);
// The Insert method, inherited from Collection, takes an
// index and an OrderItem.
//
Console.WriteLine("\nInsert(2, new OrderItem(...))");
weekly.Insert(2, new OrderItem(111033401, "Nut", 10, .5));
// The default Item property is overloaded. One overload comes
// from KeyedCollection<int, OrderItem>; that overload
// is read-only, and takes Integer because it retrieves by key.
// The other overload comes from Collection<OrderItem>, the
// base class of KeyedCollection<int, OrderItem>; it
// retrieves by index, so it also takes an Integer. The compiler
// uses the most-derived overload, from KeyedCollection, so the
// only way to access SimpleOrder by index is to cast it to
// Collection<OrderItem>. Otherwise the index is interpreted
// as a key, and KeyNotFoundException is thrown.
//
Collection<OrderItem> coweekly = weekly;
Console.WriteLine("\ncoweekly[2].Description: {0}",
coweekly[2].Description);
Console.WriteLine("\ncoweekly[2] = new OrderItem(...)");
coweekly[2] = new OrderItem(127700026, "Crank", 27, 5.98);
OrderItem temp = coweekly[2];
// The IndexOf method, inherited from Collection<OrderItem>,
// takes an OrderItem instead of a key.
//
Console.WriteLine("\nIndexOf(temp): {0}", weekly.IndexOf(temp));
// The inherited Remove method also takes an OrderItem.
//
Console.WriteLine("\nRemove(temp)");
weekly.Remove(temp);
Console.WriteLine("\nRemoveAt(0)");
weekly.RemoveAt(0);
// Increase the quantity for a line item.
Console.WriteLine("\ncoweekly(1) = New OrderItem(...)");
coweekly[1] = new OrderItem(coweekly[1].PartNumber,
coweekly[1].Description, coweekly[1].Quantity + 1000,
coweekly[1].UnitPrice);
Display(weekly);
Console.WriteLine();
weekly.Clear();
}
private static void Display(SimpleOrder order)
{
Console.WriteLine();
foreach( OrderItem item in order )
{
Console.WriteLine(item);
}
}
private static void ChangedHandler(object source,
SimpleOrderChangedEventArgs e)
{
OrderItem item = e.ChangedItem;
if (e.ChangeType==ChangeType.Replaced)
{
OrderItem replacement = e.ReplacedWith;
Console.WriteLine("{0} (quantity {1}) was replaced " +
"by {2}, (quantity {3}).", item.Description,
item.Quantity, replacement.Description,
replacement.Quantity);
}
else if(e.ChangeType == ChangeType.Cleared)
{
Console.WriteLine("The order list was cleared.");
}
else
{
Console.WriteLine("{0} (quantity {1}) was {2}.",
item.Description, item.Quantity, e.ChangeType);
}
}
}
// This class represents a simple line item in an order. All the
// values are immutable except quantity.
//
public class OrderItem
{
private int _partNumber;
private string _description;
private double _unitPrice;
private int _quantity;
public int PartNumber { get { return _partNumber; }}
public string Description { get { return _description; }}
public double UnitPrice { get { return _unitPrice; }}
public int Quantity { get { return _quantity; }}
public OrderItem(int partNumber, string description, int quantity,
double unitPrice)
{
_partNumber = partNumber;
_description = description;
_quantity = quantity;
_unitPrice = unitPrice;
}
public override string ToString()
{
return String.Format(
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}",
PartNumber, _quantity, Description, UnitPrice,
UnitPrice * _quantity);
}
}
/* This code example produces the following output:
Widget (quantity 400) was Added.
Sprocket (quantity 27) was Added.
Motor (quantity 10) was Added.
Gear (quantity 175) was Added.
110072674 400 Widget at 45.17 = 18,068.00
110072675 27 Sprocket at 5.30 = 143.10
101030411 10 Motor at 237.50 = 2,375.00
110072684 175 Gear at 5.17 = 904.75
Contains(101030411): True
weekly[101030411].Description: Motor
Remove(101030411)
Motor (quantity 10) was Removed.
Insert(2, new OrderItem(...))
Nut (quantity 10) was Added.
coweekly[2].Description: Nut
coweekly[2] = new OrderItem(...)
Nut (quantity 10) was replaced by Crank, (quantity 27).
IndexOf(temp): 2
Remove(temp)
Crank (quantity 27) was Removed.
RemoveAt(0)
Widget (quantity 400) was Removed.
coweekly(1) = New OrderItem(...)
Gear (quantity 175) was replaced by Gear, (quantity 1175).
110072675 27 Sprocket at 5.30 = 143.10
110072684 1175 Gear at 5.17 = 6,074.75
The order list was cleared.
*/
Imports System.Collections.Generic
Imports System.Collections.ObjectModel
' This class derives from KeyedCollection and shows how to override
' the protected ClearItems, InsertItem, RemoveItem, and SetItem
' methods in order to change the behavior of the default Item
' property and the Add, Clear, Insert, and Remove methods. The
' class implements a Changed event, which is raised by all the
' protected methods.
'
' SimpleOrder is a collection of OrderItem objects, and its key
' is the PartNumber field of OrderItem. PartNumber is an Integer,
' so SimpleOrder inherits KeyedCollection(Of Integer, OrderItem).
' (Note that the key of OrderItem cannot be changed; if it could
' be changed, SimpleOrder would have to override ChangeItemKey.)
'
Public Class SimpleOrder
Inherits KeyedCollection(Of Integer, OrderItem)
Public Event Changed As EventHandler(Of SimpleOrderChangedEventArgs)
' This parameterless constructor calls the base class constructor
' that specifies a dictionary threshold of 0, so that the internal
' dictionary is created as soon as an item is added to the
' collection.
'
Public Sub New()
MyBase.New(Nothing, 0)
End Sub
' This is the only method that absolutely must be overridden,
' because without it the KeyedCollection cannot extract the
' keys from the items.
'
Protected Overrides Function GetKeyForItem( _
ByVal item As OrderItem) As Integer
' In this example, the key is the part number.
Return item.PartNumber
End Function
Protected Overrides Sub InsertItem( _
ByVal index As Integer, ByVal newItem As OrderItem)
MyBase.InsertItem(index, newItem)
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Added, newItem, Nothing))
End Sub
Protected Overrides Sub SetItem(ByVal index As Integer, _
ByVal newItem As OrderItem)
Dim replaced As OrderItem = Items(index)
MyBase.SetItem(index, newItem)
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Replaced, replaced, newItem))
End Sub
Protected Overrides Sub RemoveItem(ByVal index As Integer)
Dim removedItem As OrderItem = Items(index)
MyBase.RemoveItem(index)
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Removed, removedItem, Nothing))
End Sub
Protected Overrides Sub ClearItems()
MyBase.ClearItems()
RaiseEvent Changed(Me, New SimpleOrderChangedEventArgs( _
ChangeType.Cleared, Nothing, Nothing))
End Sub
End Class
' Event argument for the Changed event.
'
Public Class SimpleOrderChangedEventArgs
Inherits EventArgs
Private _changedItem As OrderItem
Private _changeType As ChangeType
Private _replacedWith As OrderItem
Public ReadOnly Property ChangedItem As OrderItem
Get
Return _changedItem
End Get
End Property
Public ReadOnly Property ChangeType As ChangeType
Get
Return _changeType
End Get
End Property
Public ReadOnly Property ReplacedWith As OrderItem
Get
Return _replacedWith
End Get
End Property
Public Sub New(ByVal change As ChangeType, ByVal item As OrderItem, _
ByVal replacement As OrderItem)
_changeType = change
_changedItem = item
_replacedWith = replacement
End Sub
End Class
Public Enum ChangeType
Added
Removed
Replaced
Cleared
End Enum
Public Class Demo
Public Shared Sub Main()
Dim weekly As New SimpleOrder()
AddHandler weekly.Changed, AddressOf ChangedHandler
' The Add method, inherited from Collection, takes OrderItem.
'
weekly.Add(New OrderItem(110072674, "Widget", 400, 45.17))
weekly.Add(New OrderItem(110072675, "Sprocket", 27, 5.3))
weekly.Add(New OrderItem(101030411, "Motor", 10, 237.5))
weekly.Add(New OrderItem(110072684, "Gear", 175, 5.17))
Display(weekly)
' The Contains method of KeyedCollection takes TKey.
'
Console.WriteLine(vbLf & "Contains(101030411): {0}", _
weekly.Contains(101030411))
' The default Item property of KeyedCollection takes the key
' type, Integer. The property is read-only.
'
Console.WriteLine(vbLf & "weekly(101030411).Description: {0}", _
weekly(101030411).Description)
' The Remove method of KeyedCollection takes a key.
'
Console.WriteLine(vbLf & "Remove(101030411)")
weekly.Remove(101030411)
' The Insert method, inherited from Collection, takes an
' index and an OrderItem.
'
Console.WriteLine(vbLf & "Insert(2, New OrderItem(...))")
weekly.Insert(2, New OrderItem(111033401, "Nut", 10, .5))
' The default Item property is overloaded. One overload comes
' from KeyedCollection(Of Integer, OrderItem); that overload
' is read-only, and takes Integer because it retrieves by key.
' The other overload comes from Collection(Of OrderItem), the
' base class of KeyedCollection(Of Integer, OrderItem); it
' retrieves by index, so it also takes an Integer. The compiler
' uses the most-derived overload, from KeyedCollection, so the
' only way to access SimpleOrder by index is to cast it to
' Collection(Of OrderItem). Otherwise the index is interpreted
' as a key, and KeyNotFoundException is thrown.
'
Dim coweekly As Collection(Of OrderItem) = weekly
Console.WriteLine(vbLf & "coweekly(2).Description: {0}", _
coweekly(2).Description)
Console.WriteLine(vbLf & "coweekly(2) = New OrderItem(...)")
coweekly(2) = New OrderItem(127700026, "Crank", 27, 5.98)
Dim temp As OrderItem = coweekly(2)
' The IndexOf method, inherited from Collection(Of OrderItem),
' takes an OrderItem instead of a key.
'
Console.WriteLine(vbLf & "IndexOf(temp): {0}", _
weekly.IndexOf(temp))
' The inherited Remove method also takes an OrderItem.
'
Console.WriteLine(vbLf & "Remove(temp)")
weekly.Remove(temp)
Console.WriteLine(vbLf & "RemoveAt(0)")
weekly.RemoveAt(0)
' Increase the quantity for a line item.
Console.WriteLine(vbLf & "coweekly(1) = New OrderItem(...)")
coweekly(1) = New OrderItem(coweekly(1).PartNumber, _
coweekly(1).Description, coweekly(1).Quantity + 1000, _
coweekly(1).UnitPrice)
Display(weekly)
Console.WriteLine()
weekly.Clear()
End Sub
Private Shared Sub Display(ByVal order As SimpleOrder)
Console.WriteLine()
For Each item As OrderItem In order
Console.WriteLine(item)
Next item
End Sub
Private Shared Sub ChangedHandler(ByVal source As Object, _
ByVal e As SimpleOrderChangedEventArgs)
Dim item As OrderItem = e.ChangedItem
If e.ChangeType = ChangeType.Replaced Then
Dim replacement As OrderItem = e.ReplacedWith
Console.WriteLine("{0} (quantity {1}) was replaced " & _
"by {2}, (quantity {3}).", item.Description, _
item.Quantity, replacement.Description, replacement.Quantity)
ElseIf e.ChangeType = ChangeType.Cleared Then
Console.WriteLine("The order list was cleared.")
Else
Console.WriteLine("{0} (quantity {1}) was {2}.", _
item.Description, item.Quantity, e.ChangeType)
End If
End Sub
End Class
' This class represents a simple line item in an order. All the
' values are immutable except quantity.
'
Public Class OrderItem
Private _partNumber As Integer
Private _description As String
Private _unitPrice As Double
Private _quantity As Integer
Public ReadOnly Property PartNumber As Integer
Get
Return _partNumber
End Get
End Property
Public ReadOnly Property Description As String
Get
Return _description
End Get
End Property
Public ReadOnly Property UnitPrice As Double
Get
Return _unitPrice
End Get
End Property
Public ReadOnly Property Quantity() As Integer
Get
Return _quantity
End Get
End Property
Public Sub New(ByVal partNumber As Integer, _
ByVal description As String, _
ByVal quantity As Integer, _
ByVal unitPrice As Double)
_partNumber = partNumber
_description = description
_quantity = quantity
_unitPrice = unitPrice
End Sub
Public Overrides Function ToString() As String
Return String.Format( _
"{0,9} {1,6} {2,-12} at {3,8:#,###.00} = {4,10:###,###.00}", _
PartNumber, _quantity, Description, UnitPrice, _
UnitPrice * _quantity)
End Function
End Class
' This code example produces the following output:
'
'Widget (quantity 400) was Added.
'Sprocket (quantity 27) was Added.
'Motor (quantity 10) was Added.
'Gear (quantity 175) was Added.
'
'110072674 400 Widget at 45.17 = 18,068.00
'110072675 27 Sprocket at 5.30 = 143.10
'101030411 10 Motor at 237.50 = 2,375.00
'110072684 175 Gear at 5.17 = 904.75
'
'Contains(101030411): True
'
'weekly(101030411).Description: Motor
'
'Remove(101030411)
'Motor (quantity 10) was Removed.
'
'Insert(2, New OrderItem(...))
'Nut (quantity 10) was Added.
'
'coweekly(2).Description: Nut
'
'coweekly(2) = New OrderItem(...)
'Nut (quantity 10) was replaced by Crank, (quantity 27).
'
'IndexOf(temp): 2
'
'Remove(temp)
'Crank (quantity 27) was Removed.
'
'RemoveAt(0)
'Widget (quantity 400) was Removed.
'
'coweekly(1) = New OrderItem(...)
'Gear (quantity 175) was replaced by Gear, (quantity 1175).
'
'110072675 27 Sprocket at 5.30 = 143.10
'110072684 1175 Gear at 5.17 = 6,074.75
'
'The order list was cleared.
Comentarios
De forma predeterminada, KeyedCollection<TKey,TItem> incluye un diccionario de búsqueda que se crea cuando se agrega el primer elemento. Cuando se agrega un elemento a KeyedCollection<TKey,TItem>, la clave del elemento se extrae una vez y se guarda en el diccionario de búsqueda para búsquedas más rápidas. Este constructor permite invalidar ese comportamiento. Especifique 0 para crear el diccionario cuando se agregue el primer elemento, 1 para crear el diccionario cuando se agregue el segundo elemento, etc. Si especifica -1 como umbral, nunca se crea el diccionario de búsqueda.
Para colecciones muy pequeñas, la mejora de la velocidad de recuperación proporcionada por el diccionario de búsqueda podría no merecer la pena la memoria adicional requerida por el diccionario. Establecer un umbral le permite decidir cuándo se debe compensar ese equilibrio.
Nota
Dado que la KeyedCollection<TKey,TItem> clase es abstracta (MustInherit en Visual Basic), debe derivar de ella para poder usarla. En el constructor del tipo derivado, llame al constructor adecuado KeyedCollection<TKey,TItem> . No es necesario exponer funcionalidad como el comparador de igualdad o el umbral de creación del diccionario en los constructores.
Este constructor es una operación O(1).
Consulte también
Se aplica a
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