Exemples de syntaxe de requête fondée sur une méthode : conversion (LINQ to Entities)
Les exemples de cette rubrique montrent comment utiliser les méthodes ToArray, ToDictionary et ToList pour interroger le modèle de vente AdventureWorks Sales Model à l'aide de la syntaxe de requête fondée sur une méthode. Le modèle de vente AdventureWorks Sales Model utilisé dans ces exemples est construit à partir des tables Contact, Address, Product, SalesOrderHeader et SalesOrderDetail de l'exemple de base de données AdventureWorks.
Les exemples fournis dans cette rubrique utilisent les instructions using/Imports suivantes :
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
Exemple
L'exemple ci-dessous utilise la méthode ToArray pour évaluer immédiatement une séquence dans un tableau.
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
Exemple
L'exemple ci-dessous utilise la méthode ToDictionary pour évaluer immédiatement une séquence et une expression clé associée dans un dictionnaire.
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
Exemple
L'exemple ci-dessous utilise la méthode ToList pour évaluer immédiatement une séquence dans un objet List où T est de type 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));
}
}