如何获得Linq中下面的输出 [英] How to get following output in Linq

问题描述

如何模拟此SQL查询：

How to emulate this Sql query:

Select A.FID, A.SLNO, A.Date as FromDate, A1.Date ToDate
From #Test A
Inner Join #Test A1 On A.FID = A1.FID And A1.SLNO = A.SLNO + 1

其中给出：

要放弃使用此查询相同的输出：

To give the same output using this query:

var results2 = from table1 in dtSplitDates.AsEnumerable()
join table2 in dtSplitDates.AsEnumerable() on new { FID = table1.Field<int>("FID"), SLNO = table1.Field<int>("SLNO")} equals new { FID = table2.Field<int>("FID"), SLNO = table2.Field<int>("SLNO") }  into lj
from r in lj.DefaultIfEmpty()
select dtSplitDates2.LoadDataRow(new object[]
{
    r["FID"],
    r["SLNO"],
    r == null ? string.Empty : r["Dates"]
}, false);

我无法改变我的选择列表和连接条件 - 当我尝试，我得到对象引用未设置到对象的实例。有2个表 dtSplitDates 和 dtSplitDates2

这是表 dtSplitDates 现在的外观和 dtSplitDates2 是它的克隆：

This is how the table dtSplitDates looks now and dtSplitDates2 is its clone:

推荐答案

什么是dtSplitDates2？

What is dtSplitDates2 ?

可以请你分享你的表格内容。

Can you please share your table contents.

但我明白，我宁愿这个解决方案

But what I understood, I would prefer this solution

     var results2 = from table1 in dt1.AsEnumerable()
                       join table2 in dt2.AsEnumerable() on new { FID = table1.Field<int>("FID"), SLNO = table1.Field<int>("SLNO") } equals new { FID = table2.Field<int>("FID"), SLNO = table2.Field<int>("SLNO") } into lj
                       from r in lj.DefaultIfEmpty()
                       select new
                       {
                           FID = r["FID"],
                           SLNO = r["SLNO"],
                           Dates = r == null ? string.Empty : r["Date"]
                       };

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