Please suggest ways to join data tables in a dataset whose size(number of tables in dataset) is unknown

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VS2012

I am adiing excel file sheets as datatables in a dataset at runtime. Now i have to join all these data tables based on the conditions present in a list. (List contains column names that the user choose inorder to perform a left join..i.e, select.....on (table1.first item in List==table2.second item in List). I am facing this issue in Windows Form Application using C# and I am using VS2012.

Posted 22-Dec-14 18:54pm

arunkx

Updated 22-Dec-14 19:15pm

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Solution 2

I tried linq query and managed to get what I want. Thanks Maciej Los for your time. Here is what I have tried.

DataTable dtab=new DataTable();
dtab = (from a in table1.AsEnumerable()
join b in table2.AsEnumerable()
on a[Field] equals
b[Field] into g
select a).CopyToDataTable();

I placed this in a loop for all the tables in the dataset

Posted 23-Dec-14 18:00pm

arunkx

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Maciej Los · Accepted Answer · 2014-12-22T20:02:00

If you want to join data from different workbooks, the basic idea is here: How to: Get Data from Multiple Workbooks using One OleDbConnection?[^].

You did not provided a way you're fetching data into dataset. If it's a single workbook, you can use OleDbConnection[^] and OleDbCommand[^] to achieve that.
Proper query should looks like:

SQL

SELECT <FieldList>
FROM [Sheet1$] AS t1 INNER JOIN [Sheet2$] AS t2 ON t1.Field1 = t2.Field2

That's all.

[EDIT]
Please, see this: Query Expression Syntax Examples: Join Operators (LINQ to DataSet)[^]

C#

var qry = from x in dtset.Tables(1).AsEnumerable() join y in dtset.Tables(2).AsEnumerable() on x.Field<Type>("Field1") equals y.Field<Type>("Field2")
select new {
    NewField1 = x.Field<Type>(Field1),
    NewField2 = x.Field<Type>(Field2),
    NewField3 = y.Field<Type>(Field1),
    NewField4 = y.Field<Type>(Field2)
    };
foreach(var c in qry)
{
    Console.WriteLine("{0} {1} {2} [3}", c.NewField1, c.NewField2, c.NewField3, c.NewField4);
}