基于方法的查询语法示例：转换

本主题中的示例演示如何使用 ToArrayToDictionary 和 ToList 方法，利用基于方法的查询语法来查询 AdventureWorks 销售模型。 这些示例中使用的 AdventureWorks 销售模型从 AdventureWorks 示例数据库中的 Contact、Address、Product、SalesOrderHeader 和 SalesOrderDetail 等表生成。

本主题中的示例使用下面的 using/Imports 语句：

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;

Option Explicit On
Option Strict On
Imports System.Data.Objects
Imports System.Globalization

ToArray

示例

以下示例使用 ToArray 方法以立即将序列转换为数组。

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);
    }
}

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

ToDictionary

示例

以下示例使用 ToDictionary 方法以立即将序列和相关的键表达式转换为字典。

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);
}

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

ToList

示例

以下示例使用 ToList 方法以立即将序列转换为 List<T>，其中，T 属于类型 DataRow。

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));
    }
}

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

请参阅

• LINQ to Entities 中的查询