Determining duplicates in a datatable

Question

I have a data table I\'ve loaded from a CSV file. I need to determine which rows are duplicates based on two columns (product_id and owner_org_id) in t

Answer 1

You could use LINQ-To-DataSet and Enumerable.Except/Intersect:

var tbl1ID = tbl1.AsEnumerable()
        .Select(r => new
        {
            product_id = r.Field("product_id"),
            owner_org_id = r.Field("owner_org_id"),
        });
var tbl2ID = tbl2.AsEnumerable()
        .Select(r => new
        {
            product_id = r.Field("product_id"),
            owner_org_id = r.Field("owner_org_id"),
        });


var unique = tbl1ID.Except(tbl2ID);
var both = tbl1ID.Intersect(tbl2ID);

var tblUnique = (from uniqueRow in unique
                join row in tbl1.AsEnumerable()
                on uniqueRow equals new
                {
                    product_id = row.Field("product_id"),
                    owner_org_id = row.Field("owner_org_id")
                }
                select row).CopyToDataTable();
var tblBoth = (from bothRow in both
              join row in tbl1.AsEnumerable()
              on bothRow equals new
              {
                  product_id = row.Field("product_id"),
                  owner_org_id = row.Field("owner_org_id")
              }
              select row).CopyToDataTable();

---

Edit: Obviously i've misunderstood your requirement a little bit. So you only have one DataTable and want to get all unique and all duplicate rows, that's even more straight-forward. You can use Enumerable.GroupBy with an anonymous type containing both fields:

var groups = tbl1.AsEnumerable()
    .GroupBy(r => new
    {
        product_id = r.Field("product_id"),
        owner_org_id = r.Field("owner_org_id")
    });
var tblUniques = groups
    .Where(grp => grp.Count() == 1)
    .Select(grp => grp.Single())
    .CopyToDataTable();
var tblDuplicates = groups
    .Where(grp => grp.Count() > 1)
    .SelectMany(grp => grp)
    .CopyToDataTable();