Difference between two datatables based on given column

Question

I am trying to find the difference between two datatables based on a given column name. I cannot see what I am doing wrong here but when I pass two datatables that are different, I get no result.

    dt1                  dt2
ID    Percent        ID    Percent
---   -------        ---   -------
1     100            1     100
2     100            2     100
..    ...            ..    ...
50    0              50    20
..    ...            ..    ...

so, I call GetTableDiff(dt1, dt2, "Percent") and rather than getting one row (ID: 50, Percent: 20), I get nothing.

public static DataTable GetTableDiff(DataTable dt1, DataTable dt2, string sColumn)
{     
    DataTable dtDiff = new DataTable();
    try
    {
        var diff = from r1 in dt1.AsEnumerable()
                    join r2 in dt2.AsEnumerable()
                        on r1.Field<int>(sColumn)
                        equals r2.Field<int>(sColumn) into g
                    where !g.Any() // get only rows which do not have joined rows from dt2
                    select r1;

        if (diff.Count() > 0)
            dtDiff = diff.CopyToDataTable();
    }
    catch (Exception ex)
    {
    }
    return dtDiff;
}

Which column are joining on? Is sColumn the ID column in your example? If so, your example shows no rows which would not join. — Ryan Wilson
– Ryan Wilson, Commented Sep 28, 2018 at 12:25
Your rows will be joined anyway, you need to check whether Percent column's values are the same or not. — SᴇM
– SᴇM, Commented Sep 28, 2018 at 12:25
This will not produce a g if the columns don't match. All returned g's have g.Any() == true. — Olivier Jacot-Descombes
– Olivier Jacot-Descombes, Commented Sep 28, 2018 at 12:36

D-Shih · Accepted Answer · 2018-09-28 12:29:42Z

3

You need to join on "ID" instead of sColumn string, then compare your expect column name.

from r1 in dt1.AsEnumerable()
                join r2 in dt2.AsEnumerable()
                    on r1.Field<int>("ID")
                    equals r2.Field<int>("ID") 
                where r2.Field<int>(sColumn) != r1.Field<int>(sColumn) 
                select r1;

answered Sep 28, 2018 at 12:29

D-Shih

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