HOW TO：逐頁檢視查詢結果 (Entity Framework)

發行項
08/21/2008

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)。也會顯示使用下列每一個 Entity Framework 查詢技術的相同範例：

LINQ to Entities
使用 ObjectQuery<T> 的 Entity SQL
ObjectQuery<T> 的查詢產生器方法

本主題的範例是根據 Adventure Works Sales Model。若要執行此範例中的程式碼，您必須已經將 AdventureWorks Sales Model 加入到專案中，並設定您的專案使用實體架構。若要這樣做，請完成 HOW TO：手動設定 Entity Framework 專案和 HOW TO：以手動方式定義 Entity Data Model (Entity Framework) 中的程序。您也可以使用 [Entity Data Model 精靈] 定義 AdventureWorks Sales Model。如需詳細資訊，請參閱 HOW TO：使用 Entity Data Model 精靈 (Entity Framework)。

範例

這是 LINQ 到實體範例。

Using AWEntities As New AdventureWorksEntities
    'LINQ to Entities only supports Skip on ordered collections.
    Dim products As IOrderedQueryable(Of Product) = _
            AWEntities.Product.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 AWEntities = new AdventureWorksEntities())
{
    // LINQ to Entities only supports Skip on ordered collections.
    IOrderedQueryable<Product> products = AWEntities.Product
            .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);
    }
}

這是實體 SQL 範例。

Using advWorksContext As New AdventureWorksEntities()
    ' Define the parameters used to define the "page" of returned data.
    Try
        ' Create a query that takes two parameters.
        Dim esqlQuery As String = "SELECT VALUE product FROM " & _
                  " AdventureWorksEntities.Product AS product " & _
                  " order by product.ListPrice SKIP @skip LIMIT @limit"

        Dim productQuery As New ObjectQuery(Of Product)(esqlQuery, advWorksContext)
        ' Add parameters to the collection.
        productQuery.Parameters.Add(New ObjectParameter("skip", 3))
        productQuery.Parameters.Add(New ObjectParameter("limit", 5))


        ' Iterate through the page of Product items.
        For Each result As Product In productQuery
            Console.WriteLine("ID: {0} Name: {1}", _
            result.ProductID, result.Name)
        Next
    Catch ex As EntityException
        Console.WriteLine(ex.ToString())
    Catch ex As InvalidOperationException
        Console.WriteLine(ex.ToString())
    End Try
End Using

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

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

        // 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);
    }
    catch (EntityException ex)
    {
        Console.WriteLine(ex.ToString());
    }
    catch (InvalidOperationException ex)
    {
        Console.WriteLine(ex.ToString());
    }
}

這是查詢產生器方法範例。

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

    Try
        ' 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) = advWorksContext.Product _
            .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
    Catch ex As EntitySqlException
        Console.WriteLine(ex.ToString())
    End Try
End Using

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

    try
    {
        // 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 = advWorksContext.Product
            .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);
    }
    catch (EntitySqlException ex)
    {
        Console.WriteLine(ex.ToString());
    }
}

另請參閱

共用方式為

HOW TO：逐頁檢視查詢結果 (Entity Framework)

範例

另請參閱

參考

概念

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