Question

我很难将SQL转换为LINQ语句。

这是SQL语句：

SELECT * FROM dataTableA INNER JOIN dataTableB ON dataTableA.ID =dataTableB.SNo OR 
         dataTableA.Address = dataTableB.Address 
         WHERE (dataTableA.Name = dataTableB.UserName)

OR部分On部分我不知道如何编写LINQ语法。我在没有OR条件的情况下试过了以下报价。请建议。

var matches = from rowA  in dataTableA.AsEnumerable()
                join rowB in dataTableB.AsEnumerable()
                on  rowA["ID"].ToString().Trim() equals rowB["SNo"].ToString().Trim()  
                where  rowA["Name"].ToString().Trim() == rowB["UserName"].ToString().Trim() 
                select new { rowA, rowB } ;

Answer 1

试试这种方式

var matches = from rowA  in dataTableA.AsEnumerable()
              from  rowB in dataTableB.AsEnumerable().Where(x=>x.SNo==rowA.ID || x.Address ==rowA.Address) .AsEnumerable()              
               where  rowA["Name"].ToString().Trim() == rowB["UserName"].ToString().Trim() 
                    select new { rowA, rowB } ;

Answer 2

您可以使用复合键加入ID 和 Adress https://msdn.microsoft.com/en-us/library/bb907099.aspx

dataTableA.AsEnumerable().join(dataTableB.AsEnumerable(),
  ta => new {ta.ID, ta.Adress}, tb => new {tb.SNo, tb.Adress}, 
  (ta, tb) => new {ta, tb})

如果您想加入ID 或 Adress，您可以联合2个联接，我认为仍然应该比n快where s：Why is LINQ JOIN so much faster than linking with WHERE?

dataTableA.AsEnumerable().join(dataTableB.AsEnumerable(),
  ta => ta.ID, tb => tb.SNo, (ta, tb) => new {ta, tb})
.union(dataTableA.AsEnumerable().join(dataTableB.AsEnumerable(),
  ta => ta.Adress, tb => tb.Adress, (ta, tb) => new {ta, tb}))

Answer 3

    var matches = dataTableA.AsEnumerable()
        .Select(a => new {
                    RowA = a,
                    RowB = dataTableB.AsEnumerable().FirstOrDefault(b => ((b["SNo"] == a["ID"]) || (b["Address"].Equals(a["Address"]))))
                })
        .Where(pair => pair.RowB != null) //to replicate the inner-join
        .Where(pair => pair.RowA["Name"].Equals(pair.RowB["Username"]));

Answer 4

在对Mukesh Kalgude的回答进行微小修改后，问题解决了。下面是最终的工作代码。感谢所有人的善意建议。

var matches = from rowA  in dataTableA.AsEnumerable()
              from  rowB in    dataTableB.AsEnumerable().Where(x=>x["SNo"]==rowA["ID"] || x["Address"]==rowA["Address"]) .AsEnumerable()              
             where  rowA["Name"].ToString().Trim() == rowB["UserName"].ToString().Trim() 
             select new { rowA, rowB } ;

LINQ：如何为＆＃34; on＆＃34;写出多个条件caluse？

4 个答案: