HOW TO：逐頁檢視查詢結果 (Entity Framework)

發行項
02/28/2011

本主題將說明如何為查詢結果分頁。此範例會在略過查詢結果的前三個 Product 物件之後取得五個物件 (根據 Product.ListPrice 排序)。使用下列每一個 Entity Framework 查詢技術也會顯示相同的範例：

LINQ to Entities
Entity SQL with ObjectQuery<T>
Query builder methods of ObjectQuery<T>

本主題的範例根據 Adventure Works Sales Model。若要執行此主題中的程式碼，您必須已經將 Adventure Works Sales Model 加入到專案中，並設定您的專案使用 Entity Framework。如需詳細資訊，請參閱 HOW TO：使用實體資料模型精靈 (Entity Framework) 或 HOW TO：手動設定 Entity Framework 專案及 HOW TO：手動設定 Entity Framework 專案。

範例

這是 LINQ to Entities 範例。

Using context As New AdventureWorksEntities
    'LINQ to Entities only supports Skip on ordered collections.
    Dim products As IOrderedQueryable(Of Product) = _
            context.Products.OrderBy(Function(p) p.ListPrice)

    Dim allButFirst3Products As IQueryable(Of Product) = products.Skip(3)

    Console.WriteLine("All but first 3 products:")
    For Each product As Product In allButFirst3Products
        Console.WriteLine("Name: {0} \t ID: {1}", _
                product.Name, _
                product.ProductID)
    Next
End Using

using (AdventureWorksEntities context = new AdventureWorksEntities())
{
    // LINQ to Entities only supports Skip on ordered collections.
    IOrderedQueryable<Product> products = context.Products
            .OrderBy(p => p.ListPrice);

    IQueryable<Product> allButFirst3Products = products.Skip(3);

    Console.WriteLine("All but first 3 products:");
    foreach (Product product in allButFirst3Products)
    {
        Console.WriteLine("Name: {0} \t ID: {1}",
            product.Name,
            product.ProductID);
    }
}

這是 Entity SQL 範例。

Using context As New AdventureWorksEntities()
    ' Create a query that takes two parameters. 
    Dim queryString As String = "SELECT VALUE product FROM AdventureWorksEntities.Products AS product " & _
        " order by product.ListPrice SKIP @skip LIMIT @limit"

    Dim productQuery As New ObjectQuery(Of Product)(queryString, context)

    ' Add parameters to the collection. 
    productQuery.Parameters.Add(New ObjectParameter("skip", 3))
    productQuery.Parameters.Add(New ObjectParameter("limit", 5))

    ' Iterate through the collection of Contact items. 
    For Each result As Product In productQuery
        Console.WriteLine("ID: {0}; Name: {1}", result.ProductID, result.Name)
    Next
End Using

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    // Create a query that takes two parameters.
    string queryString =
        @"SELECT VALUE product FROM 
          AdventureWorksEntities.Products AS product 
          order by product.ListPrice SKIP @skip LIMIT @limit";

    ObjectQuery<Product> productQuery =
        new ObjectQuery<Product>(queryString, context);

    // Add parameters to the collection.
    productQuery.Parameters.Add(new ObjectParameter("skip", 3));
    productQuery.Parameters.Add(new ObjectParameter("limit", 5));

    // Iterate through the collection of Contact items.
    foreach (Product result in productQuery)
        Console.WriteLine("ID: {0}; Name: {1}",
        result.ProductID, result.Name);
}

這是查詢產生器方法範例。

Using context As New AdventureWorksEntities()
    ' Define the parameters used to define the "page" of returned data. 
    Dim skipValue As Integer = 3
    Dim limitValue As Integer = 5

    ' Define a query that returns a "page" or the full 
    ' Product data using the Skip and Top methods. 
    ' When Top() follows Skip(), it acts like the LIMIT statement. 
    Dim query As ObjectQuery(Of Product) = _
        context.Products.Skip("it.ListPrice", "@skip", _
            New ObjectParameter("skip", skipValue)).Top("@limit", New ObjectParameter("limit", limitValue))

    ' Iterate through the page of Product items. 
    For Each result As Product In query
        Console.WriteLine("ID: {0}; Name: {1}", result.ProductID, result.Name)
    Next
End Using

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    // Define the parameters used to define the "page" of returned data.
    int skipValue = 3;
    int limitValue = 5;

    // Define a query that returns a "page" or the full 
    // Product data using the Skip and Top methods. 
    // When Top() follows Skip(), it acts like the LIMIT statement.
    ObjectQuery<Product> query = context.Products
        .Skip("it.ListPrice", "@skip",
                new ObjectParameter("skip", skipValue))
        .Top("@limit", new ObjectParameter("limit", limitValue));

    // Iterate through the page of Product items.
    foreach (Product result in query)
        Console.WriteLine("ID: {0}; Name: {1}",
        result.ProductID, result.Name);
}

HOW TO：逐頁檢視查詢結果 (Entity Framework)

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