小巧玲珑.分页

Question

我正在尝试Dapper ORM,我正在查询帖子表.

但我想获得分页结果......

1 - 我该怎么做？这不是帮手吗？

2 - Dapper Query可以返回IQueryable吗？

谢谢你,米格尔

Answer 1

您没有指定数据库或版本.如果你足够幸运,能够使用该品牌新的SQL Server 2012,并访问MSDN,您可以用崭新的OFFSET和FETCH关键字.以下查询将跳过20条记录并返回下一条5条记录.

SELECT * FROM [Posts]
ORDER BY [InsertDate]
OFFSET 20 ROWS
FETCH NEXT 5 ROWS ONLY

有关详细信息,请查看http://msdn.microsoft.com/en-us/library/ms188385(v=sql.110).aspx#Offset.

此外,复制Massive的方式并为IDbConnection编写自己的扩展方法也很容易.这是Massive的代码.

var query = string.Format("SELECT {0} FROM (SELECT ROW_NUMBER() OVER (ORDER BY {2}) AS Row, {0} FROM {3} {4}) AS Paged ", columns, pageSize, orderBy, TableName, where);

Answer 2

1)Dapper没有内置的分页功能.但是在查询中直接实现它并不困难.例:

SELECT  *
FROM    ( SELECT    ROW_NUMBER() OVER ( ORDER BY InsertDate) AS RowNum, *
          FROM      Posts
          WHERE     InsertDate >= '1900-01-01'
        ) AS result
WHERE   RowNum >= 1 // *your pagination parameters
    AND RowNum < 20  //*
ORDER BY RowNum

需要SQL Server 2005+

2)Dapper返回一个IEnumerable<T>.

Answer 3

这是使用 C# 和 Dapper 的完整工作版本。

/// <summary>
    /// Gets All People
    /// </summary>
    /// <returns>List of People</returns>
    public IEnumerable<Person> GetAllPeople(Pager pager)
    {
        var sql = (@" select * from [dbo].[Person]
                      order by [PeplNo]
                      OFFSET      @Offset ROWS 
                      FETCH NEXT  @Next   ROWS ONLY");

        using (IDbConnection cn = Connection)
        {
            cn.Open();

            var results = cn.Query<Person>(sql,pager);

            return results;
        }
    }


public class Pager
{
    public int Page { get; set; }
    public int PageSize { get; set; }

    public int Offset { get; set; }
    public int Next { get; set; }

    public Pager(int page, int pageSize = 10)
    {
        Page = page < 1 ? 1 : page;
        PageSize = pageSize < 1 ? 10 : pageSize;

        Next = pageSize;
        Offset = (Page - 1) * Next;
    }

}