c# - PagedList 不会在 asp.net mvc 中进行真正的分页

Question

在我的项目中，我需要对查询进行分页。我使用 Entity Framework 从数据库获取数据。 This video on youtube解释如何对查询进行分页。简而言之，视频说您所要做的就是将 PagedList.Mvc 安装到您的项目和此代码

.ToPagedList(PageNumber,PageSize)

首先，这似乎对我有用，但我发现(在使用 Sql server profile 检查 Entity Framework 传递给 sql server 的内容之后) Entity Framework 向 sql server 询问所有数据，然后选择需要的数据。更清楚地说，这是我在 C#(服务器端)上的代码

var messages = db.Messages.Where(x => x.User1 == 1 && x.User2 == 2).OrderBy(x=>x.Date).ToList().ToPagedList(1,4);

传递给sql server的是这样的:

exec sp_executesql N'SELECT 
    [Project1].[Id] AS [Id], 
    [Project1].[User1] AS [User1], 
    [Project1].[User2] AS [User2], 
    [Project1].[Direction] AS [Direction], 
    [Project1].[TextContent] AS [TextContent], 
    [Project1].[ReadBit] AS [ReadBit], 
    [Project1].[Date] AS [Date], 
    [Project1].[ReceivedBit] AS [ReceivedBit]
    FROM ( SELECT 
        [Extent1].[Id] AS [Id], 
        [Extent1].[User1] AS [User1], 
        [Extent1].[User2] AS [User2], 
        [Extent1].[Direction] AS [Direction], 
        [Extent1].[TextContent] AS [TextContent], 
        [Extent1].[ReadBit] AS [ReadBit], 
        [Extent1].[ReceivedBit] AS [ReceivedBit], 
        [Extent1].[Date] AS [Date]
        FROM [Messages].[Messages] AS [Extent1]
        WHERE ([Extent1].[User1] = @p__linq__0) AND ([Extent1].[User2] = @p__linq__1)
    )  AS [Project1]
    ORDER BY [Project1].[Date] ASC',N'@p__linq__0 int,@p__linq__1 int',@p__linq__0=1,@p__linq__1=2

所以sql server中没有分页，我认为这样的分页没有任何优势。我是否错过了一些无法使其发挥作用的东西？或者就是这样工作？

Answer 1

PagedList附加Skip()和Take()到您的查询(计算从 PageNumber 和 PageSize 跳过的行数)。但查询应该是原来的IQueryable这些添加内容会到达查询提供程序并影响 SQL 转换。 ToList断开此连接。