Linq在多列上联接数据表

Question

I have a linq statements that takes two datatables and joins them together on the id column of each table. My issue is that sometimes the value that I am joining is in a different column in the datatable and I would like to be able to have the statement as is and to look at the other column as well:

Existing:

Datatable1.AsEnumerable()
           .Join(Datatable2.AsEnumerable(),
               dt1Row => Datatable1.Field<string>(rowid),
               dt2Row=> Datatable2.Field<string>(rowid),
               (dt1Row , dt2Row) => new { dt1Row , dt2Row}).ToList()
           .ForEach(o => {
               o.dt1Row.SetField(o.dt1Row.Table.Columns["name"].Ordinal, o.dt2Row.Field<string>("name1"));

           });

Datatable1.AsEnumerable()
           .Join(Datatable2.AsEnumerable(),
              //Trying to work out?
              ( dt1Row => Datatable1.Field<string>("rowid"),
               dt2Row=> Datatable2.Field<string>("rowid"))
              || ( dt1Row => Datatable1.Field<string>("rowid"),
               dt2Row=> Datatable2.Field<string>("name")),
               (dt1Row , dt2Row) => new { dt1Row , dt2Row}).ToList()

           .ForEach(o => {
               o.dt1Row.SetField(o.dt1Row.Table.Columns["name"].Ordinal, o.dt2Row.Field<string>("name1"));

           });

Answer 1

sorry for delay, you can use this approach:

var dt1 = DataTable1.AsEnumerable();
var dt2 = DataTable2.AsEnumerable();

 var query = (from dt1Row in dt1
              from dt2Row in dt2
              where dt1Row["rowid"] == dt2Row["rowid"] ||
                    dt1Row["rowid"] == dt2Row["name"]

              select new
              {
                  dt1Row,
                  dt2Row
              });

Answer 2

you can use iif statement:

.Join(Datatable2.AsEnumerable(),
      dt1Row => Datatable1.Field<string>("rowid"),
      dt2Row => condition ? Datatable2.Field<string>("rowid") : Datatable2.Field<string>("name"),
      (dt1Row , dt2Row) => new { dt1Row , dt2Row})

condition must return a boolean value

Answer 3

Added another Linq statement in the Join for Datatable2 using any dt.Any() as the condition

Join(Datatable2.AsEnumerable(),
  dt1Row => Datatable1.Field<string>("rowid"),
  dt2Row => Datatable1.AsEnumerable.Any(x => x.Field<string>("rowid") == Datatable2.Field<string>("rowid"))
? Datatable2.Field<string>("rowid") : Datatable2.Field<string>("name"),
  (dt1Row , dt2Row) => new { dt1Row , dt2Row})