Linq进行多项选择 [英] Linq for multiple select

问题描述

朋友们，
我需要Linq查询才能从3个表中选择数据.

我用C#代码实现.但是我需要在LINQ Query中进行开发.

foreach(dtChapter.Rows中的DataRow drChapters)
{
DataRow dr = dtPlanInfo.NewRow();
foreach(dtMileStones.Rows中的DataRow drMileStone)
{
dr ["Chapter"] = drChapters ["Chapter"].ToString();
DataRow [] drStages = dtStages.Select("Chapter =""+ drChapters [" Chapter].ToString()+"''和MilestoneDesc =" + drMileStone ["MilestoneDesc"] +''")；
foreach(drStages中的DataRow drs)
{
dr [drMileStone ["MilestoneDesc"].ToString()+"PlanDate"] = drs ["PlanDate"];
dr [drMileStone ["MilestoneDesc"].ToString()+"ActualDate"] = drs ["ActualDate"];
dr [drMileStone ["MilestoneDesc"].ToString()+"Remarks"] = drs ["Remarks"].ToString();
dr [drMileStone ["MilestoneDesc"].ToString()+"RevisedCount"] = drs ["RevisedCount"];
dr [drMileStone ["MilestoneDesc"].ToString()+"LastTimeRevised"] = drs ["LastRevisedPlanDate"];
}
}
dtPlanInfo.Rows.Add(dr);
}

涉及的表是

第

Ch1

Ch2

MileStone

MileStoneDesc

M1

M2

StageId	PlanDate	ActualDate	备注	第	MilestoneDesc	revisedCount	LastTimeRevised
1	12/9/2012	2012/12/15	test	Ch1	M1
2	3/2/2013	5/6/2013	test2	ch2	M2

我需要结果为

章节	M1Plan	M1Actual	M1Remark	M1RevisedCount	M1LastRevised	M2Plan	M2Actual	M2Remark	M2RevisedCount	M2LastRevised
ch1	2012/12/9	2012/12/15		test
ch2						3/2/2013	5/6/2013	test2

请提供Linq查询以获取此结果.

Hi friends,
i need the Linq Query to select datas from 3 Tables.

I acheived in c# Code. But i need to develop in LINQ Query.

foreach (DataRow drChapters in dtChapter.Rows)
{
DataRow dr = dtPlanInfo.NewRow();
foreach (DataRow drMileStone in dtMileStones.Rows)
{
dr["Chapter"] = drChapters["Chapter"].ToString();
DataRow[] drStages = dtStages.Select("Chapter=''" + drChapters["Chapter"].ToString() + "'' and MilestoneDesc=''" + drMileStone["MilestoneDesc"] + "''");
foreach (DataRow drs in drStages)
{
dr[drMileStone["MilestoneDesc"].ToString() + "PlanDate"] = drs["PlanDate"];
dr[drMileStone["MilestoneDesc"].ToString() + "ActualDate"] = drs["ActualDate"];
dr[drMileStone["MilestoneDesc"].ToString() + "Remarks"] = drs["Remarks"].ToString();
dr[drMileStone["MilestoneDesc"].ToString() + "RevisedCount"] = drs["RevisedCount"];
dr[drMileStone["MilestoneDesc"].ToString() + "LastTimeRevised"] = drs["LastRevisedPlanDate"];
}
}
dtPlanInfo.Rows.Add(dr);
}

The Tables involved are

Chapter

Ch1

Ch2

MileStone

MileStoneDesc

M1

M2

StageId	PlanDate	ActualDate	Remarks	Chapter	MilestoneDesc	revisedCount	LastTimeRevised
1	12/9/2012	15/12/2012	test	Ch1	M1
2	3/2/2013	5/6/2013	test2	ch2	M2

I need the Result as

Chapter	M1Plan	M1Actual	M1Remark	M1RevisedCount	M1LastRevised	M2Plan	M2Actual	M2Remark	M2RevisedCount	M2LastRevised
ch1	12/9/2012	15/12/2012		test
ch2						3/2/2013	5/6/2013	test2

Please provide me the Linq Query to get this result.

推荐答案

以下带有Method (Fluent) syntax的LINQ查询可用于实现上述结果

The following LINQ query with Method (Fluent) syntax can be used to achieve the above result

IEnumerable<dataset1.dtplaninforow> planInfos = DataSetInstance.dtStages.AsEnumerable()
    .Where(st => 
        DataSetInstance.dtChapter.Any(ch => ch.Chapter==st.Chapter) &&
        DataSetInstance.dtMileStones.Any(ms => ms.MilestoneDesc==st.MilestoneDesc))
    .Select(st => {
        var dr = DataSetInstance.dtPlanInfo.NewdtPlanInfoRow();
        dr.Chapter = st.Chapter;
        dr[string.Format("{0}Plan", st.MilestoneDesc)] = st.PlanDate;
        dr[string.Format("{0}Actual", st.MilestoneDesc)] = st.ActualDate;
        dr[string.Format("{0}Remark", st.MilestoneDesc)] = st.Remarks;
        dr[string.Format("{0}RevisedCount", st.MilestoneDesc)] = st.revisedCount;
        dr[string.Format("{0}LastRevised", st.MilestoneDesc)] = st.LastTimeRevised;
        return dr;
    });
planInfos.CopyToDataTable(DataSetInstance.dtPlanInfo, LoadOption.PreserveChanges);

在PlanInfo 表的新行中设置值时，使用LINQ query expression syntax很难获得上述结果.

It is somewhat difficult to get the above result using the LINQ query expression syntax in setting the values in new row of PlanInfo table.

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