Ejemplos de sintaxis de consulta basada en métodos: conversión (LINQ to Entities)
Los ejemplos de este tema muestran cómo se utilizan los métodos ToArray, ToDictionary y ToList para consultar el modelo AdventureWorks Sales utilizando la sintaxis de las consultas basadas en métodos. El modelo AdventureWorks Sales que se usa en estos ejemplos se crea a partir de las tablas Contact, Address, Product, SalesOrderHeader y SalesOrderDetail de la base de datos de ejemplo AdventureWorks.
Los ejemplos de este tema usan las instrucciones using/Imports siguientes:
Option Explicit On
Option Strict On
Imports System.Data.Objects
Imports System.Globalization
using System;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Objects;
using System.Globalization;
using System.Data.EntityClient;
using System.Data.SqlClient;
using System.Data.Common;
ToArray
Ejemplo
En el ejemplo siguiente se usa el método ToArray para evaluar de forma inmediata una secuencia en una matriz.
Using context As New AdventureWorksEntities
Dim products As ObjectSet(Of Product) = context.Products
Dim prodArray As Product() = ( _
From product In products _
Order By product.ListPrice Descending _
Select product).ToArray()
Console.WriteLine("The list price from highest to lowest:")
For Each prod As Product In prodArray
Console.WriteLine(prod.ListPrice)
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Product> products = context.Products;
Product[] prodArray = (
from product in products
orderby product.ListPrice descending
select product).ToArray();
Console.WriteLine("Every price from highest to lowest:");
foreach (Product product in prodArray)
{
Console.WriteLine(product.ListPrice);
}
}
ToDictionary
Ejemplo
En el ejemplo siguiente se utiliza el método ToDictionary para evaluar de forma inmediata una secuencia y una expresión de clave relacionada en un diccionario.
Using context As New AdventureWorksEntities
Dim products As ObjectSet(Of Product) = context.Products
Dim scoreRecordsDict As Dictionary(Of String, Product) = _
products.ToDictionary(Function(record) record.Name)
Console.WriteLine("Top Tube's ProductID: {0}", _
scoreRecordsDict("Top Tube").ProductID)
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Product> products = context.Products;
Dictionary<String, Product> scoreRecordsDict = products.
ToDictionary(record => record.Name);
Console.WriteLine("Top Tube's ProductID: {0}",
scoreRecordsDict["Top Tube"].ProductID);
}
ToList
Ejemplo
En el ejemplo siguiente se utiliza el método ToList para evaluar inmediatamente una secuencia en List, donde T es de tipo DataRow.
Using context As New AdventureWorksEntities
Dim products As ObjectSet(Of Product) = context.Products
Dim prodList As List(Of Product) = ( _
From product In products _
Order By product.Name _
Select product).ToList()
Console.WriteLine("The product list, ordered by product name:")
For Each prod As Product In prodList
Console.WriteLine(prod.Name.ToLower(CultureInfo.InvariantCulture))
Next
End Using
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Product> products = context.Products;
List<Product> query =
(from product in products
orderby product.Name
select product).ToList();
Console.WriteLine("The product list, ordered by product name:");
foreach (Product product in query)
{
Console.WriteLine(product.Name.ToLower(CultureInfo.InvariantCulture));
}
}