以方法為基礎的查詢語法範例：轉換 (LINQ to Entities)

本主題中的範例將示範如何使用 ToArray、ToDictionary 和 ToList 方法，透過以方法為基礎的查詢語法來查詢 AdventureWorks Sales Model。 這些範例中使用的 AdventureWorks Sales Model 是從 AdventureWorks 範例資料庫中的 Contact、Address、Product、SalesOrderHeader 和 SalesOrderDetail 資料表所建立。

此主題中的範例將使用下列 using/Imports 陳述式：

Option Explicit On
Option Strict On
Imports L2EExamplesVB.AdventureWorksModel
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 AdventureWorksModel;
using System.Globalization;

如需詳細資訊，請參閱 HOW TO：在 Visual Studio 中建立 LINQ to Entities 專案。

ToArray

範例

下列範例會使用 ToArray 方法，立即將序列 (Sequence) 評估為陣列。

Using AWEntities As New AdventureWorksEntities
    Dim products As ObjectQuery(Of Product) = AWEntities.Product

    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 AWEntities = new AdventureWorksEntities())
{
    ObjectQuery<Product> products = AWEntities.Product;

    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

範例

下列範例會使用 ToDictionary 方法，立即將序列和相關的索引鍵運算式評估為字典。

Using AWEntities As New AdventureWorksEntities
    Dim products As ObjectQuery(Of Product) = AWEntities.Product

    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 AWEntities = new AdventureWorksEntities())
{
    ObjectQuery<Product> products = AWEntities.Product;

    Dictionary<String, Product> scoreRecordsDict = products.
            ToDictionary(record => record.Name);

    Console.WriteLine("Top Tube's ProductID: {0}",
            scoreRecordsDict["Top Tube"].ProductID);
}

ToList

範例

下列範例會使用 ToList 方法，立即將序列評估為 List，其中 T 的型別為 DataRow。

Using AWEntities As New AdventureWorksEntities
    Dim products As ObjectQuery(Of Product) = AWEntities.Product

    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 AWEntities = new AdventureWorksEntities())
{
    ObjectQuery<Product> products = AWEntities.Product;

    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));
    }
}

另請參閱

概念

以方法為基礎的查詢語法範例 (LINQ to Entities)