Question

I am attempting to get distinct values from a datatable column. here is my code..

var sourceItems = ds.Tables[0].AsEnumerable()
                              .GroupBy(x => x.Field<string>("Source").ToString())
                              .Select(x => x.First());
ddlSource.DataSource = sourceItems;
ddlSource.DataBind();

This code is returning 4 rows of System.Data.DataRow as the values. I need the actual values stored in the rows not the row type. Also is this code a proper way to grab only distinct values in the column?

Answer 1

I would do something like this:

var sourceItems = ds.Tables[0].AsEnumerable()
                              .Select(x => x.Field<string>("Source"))
                              .Distinct()
                              .ToList();

Note that .ToList() can be skipped, but of course it depends on what the DataSource property of the ddlSource object is able to accept. If It’s a winforms control I suspect ToList is necessary.

Your code does basically the same as this one, but you must change the last Select into Select(x => x.Key) to select the values that are used to group the rows, and not the first row.
Also your code has more overhead than using Distinct, since GroupBy creates subgroups of the original collection.