Question

My Datatable 1 (dtOutput) Format (termid,faultid,faultdesc,faulttime,devicetype)

My Datatable 2 (dtOpenEvent) Format (termid,faultid)

I want to retrieve those values which are present in Datatable 2 but not in Datatable 1…based on two columns (termid,faultid) no table have primary keys.

I Searched on net and find code which return diff between two data table…

Now how can i retrieve column values from it ? either in another data table or in string variable

Code :-

DataTable dtOpenEvent;
dtOpenEvent = Generix.getOpenEvents(ref Connection);
DataTable dtOutput;
dtOutput = Generix.getFeedData(ref Connection);
var matched = from table1 in dtOpenEvent.AsEnumerable()
              join table2 in dtOutput.AsEnumerable() on table1.Field<string>("ATM") equals table2.Field<string>("termid")
              where table1.Field<int>("Event") == table2.Field<int>("faultid") 
              select table1;
var missing = from table1 in dtOpenEvent.AsEnumerable()
              where !matched.Contains(table1)
              select table1;

Answer 1

you can remove all of the columns in dt1 and then do except.

like this:
var diff =dt2.AsEnumerable().Except(dt1.AsEnumerable(), DataRowComparer.Default);

full example:

            DataTable dt1 = new DataTable();
            DataTable dt2 = new DataTable();

            dt1.Columns.Add("termid", typeof(Int32));
            dt1.Columns.Add("faultid", typeof(Int32));
            dt1.Columns.Add("faultdesc");
            dt2.Columns.Add("termid", typeof(Int32));
            dt2.Columns.Add("faultid", typeof(Int32));

            dt1.Rows.Add(1,2,"desc");
            dt1.Rows.Add(3, 4, "desc");
            dt1.Rows.Add(5, 6, "desc");
            dt2.Rows.Add(1, 2);
            dt2.Rows.Add(3, 4);
            dt2.Rows.Add(7, 8);

            dt1.Columns.Remove("faultdesc");
            var diff =dt2.AsEnumerable().Except(dt1.AsEnumerable(), DataRowComparer.Default);

            foreach (var row in diff)
            {
                Console.WriteLine(row["termid"] + " " + row["faultid"]); //prints 7 8
            }  

or instead of removing columns you can select them through linq or dataview like this:

        var view = new DataView(dt1);
        DataTable dt3 = view.ToTable(true, "termid", "faultid");    

modified example:

            DataTable dt1 = new DataTable();
            DataTable dt2 = new DataTable();

            dt1.Columns.Add("termid", typeof(Int32));
            dt1.Columns.Add("faultid", typeof(Int32));
            dt1.Columns.Add("faultdesc");
            dt2.Columns.Add("termid", typeof(Int32));
            dt2.Columns.Add("faultid", typeof(Int32));

            dt1.Rows.Add(1,2,"desc");
            dt1.Rows.Add(3, 4, "desc");
            dt1.Rows.Add(5, 6, "desc");
            dt2.Rows.Add(1, 2);
            dt2.Rows.Add(3, 4);
            dt2.Rows.Add(7, 8);

            var view = new DataView(dt1);
            DataTable dt3 = view.ToTable(true, "termid", "faultid");
            var diff =dt2.AsEnumerable().Except(dt3.AsEnumerable(), DataRowComparer.Default);

            foreach (var row in diff)
            {
                Console.WriteLine(row["termid"] + " " + row["faultid"]);
            }