Question

I have a dataset with three tables in it. I want to compare a column item from one table against column items from the other two but to do this I am using nested foreach loops. The code is returning way more data than it should be so I have a feeling I messed something up; also I’m sure there is a better/cleaner way to do this, feel free to let me know.

foreach (DataRow row in dataSet.Tables["Taxonomy"].Rows)
            {
                var projectTypes = row["ProjectType"].ToString();
                var tier3 = row["Tier3Project"].ToString();
                if (tier3.Equals(""))
                    tier3 = "null";
                Console.WriteLine(projectTypes);

                foreach (DataRow dRow in dataSet.Tables["DefaultEventTypes"].Rows)
                {
                    var name = dRow["name"].ToString();
                    if (name.Equals(""))
                        name = "null";

                    /****** Begin Comparisons ******/
                    if (projectTypes.Trim().ToLower().Equals(name.Trim().ToLower()))
                    {
                        foreach (DataRow sRow in dataSet.Tables["ScheduleEvents"].Rows)
                        {
                            var nameShort = sRow["nameShort"].ToString();

                            /****** Compare to ScheduleEvent ******/
                            if (projectTypes.Trim().ToLower().Equals(nameShort.Trim().ToLower()))
                            {
                                //Update both DefaultEventType and ScheduleEvent
                                Console.WriteLine(projectTypes + "     " + name + "     " + tier3);
                                counter++;
                            }
                            else
                            {

                            }
                        }
                    }
                    else
                    {
                        foreach (DataRow sRow in dataSet.Tables["ScheduleEvents"].Rows)
                        {
                            var nameShort = sRow["nameShort"].ToString();

                            /****** Compare to ScheduleEvent ******/
                            if (projectTypes.Trim().ToLower().Equals(nameShort.Trim().ToLower()))
                            {
                                //Update ScheduleEvent
                            }
                        }
                    }
                    /****** End Comparisons ******/
                }
            }

I can clarify if needed, thanks!

Edit:

I want to pull an item from table ‘Taxonomy’ and then compare it to every row in table ‘DefaultEventTypes’. If there is a match, I then want to compare the ‘Taxonomy’ item to every row in ‘ScheduleEvent’.

Eventually I want to add in update statements to change matching items to a new name and save the tables back to the database.

It seems to be doing comparisons but the number of values it’s returning is far too large.

Answer 1

dataSet.Tables["Table1"].AsEnumerable().Select(r => r.Field<string>("Field1")).Intersect(
dataSet.Tables["Table2"].AsEnumerable().Select(r => r.Field<string>("Field2"))).Intersect(
dataSet.Tables["Table3"].AsEnumerable().Select(r => r.Field<string>("Field3")));

Something like that…didn’t test this, though

PS: this should return you a set of values, that are present in all 3 tables in respective columns.

Answer to comment:
Well, you have enough information to update things you want.

var valuesThatRepeat = GetWhatYouNeedUsingCodeAbove();
foreach (var value in valuesThatRepeat)
{
    var rows = dataSet.Tables["Table2"].AsEnumerable().Where(r => ((string)r["Column2"]).Equals(value));            
    foreach(var row in rows)
    {
        row["Column2"] = (string)r["Column2"] + "of_row_with_id_" + (string)r["Id"]; // update the value with whatever you want
    }
}

This example will update all the values in the second table so that they are no longer similar to those in other 2 tables. PS: again, didn’t test that. syntax error are possible