Question

I am trying to search the datatable for non-unique values and I keep getting this error

Filter expression ‘PROV_NEW’ does not evaluate to a Boolean term.

when I run it.

This is my code:

public class GetData
{
    datalogiclayer.TableSetup dal;
    DataSet ds;

    public delegate void InvalidTableDataDelegate(string ErrorMessage);
    public event InvalidTableDataDelegate InvalidTableData;

    public delegate void SetupDataLoadedDelegate(System.Data.DataSet dv, string TableName);
    public event SetupDataLoadedDelegate SetupDataLoaded;

    public GetData()
    {
        dal = new datalogiclayer.TableSetup();
    }

    public void Update(DataSets.Setup ds)
    {
        try
        {
            string errMsg = string.Empty;

            if (ValidateTable(ds.SETUP_MWPROV, out errMsg))
            {
                dal.UpdateDatabase(ds);
            }
            else
            {
                if (InvalidTableData != null)
                    InvalidTableData(errMsg);
            }
        }
        catch (Exception)
        {
            throw;
        }
    }

    private bool ValidateTable(DataSets.Setup.SETUP_MWPROVDataTable dt, out string TableIssues)
    {
        try
        {
            //NewCode not used for other row
            DataRow[] result = dt.Select("PROV_NEW = ''");
            DataRow[] dupresults = dt.Select("PROV_NEW");
            TableIssues = string.Empty;
            DataTable dtTemp = dt.DefaultView.ToTable(true, "NEW_PROV");

            if (dupresults.Length == 0)
            {
                return true;
            }
            else
            {
                IEnumerable<DataRow> uniqueCodes = dupresults.AsEnumerable().Distinct(DataRowComparer.Default);

                Console.WriteLine("Unique Provider Codes:");

                foreach (DataRow NEW_PROV in uniqueCodes)
                {
                    Console.WriteLine(NEW_PROV.Field<Int32>("PROV_NEW"));
                }

                return false;
            }          
        }
        catch (Exception)
        {
            throw;
        }
    }
}

So as you can see I have it searching for unique rows in the datatable, when the exception is being thrown is when I actually go to save the data. And it gives the error that is up above.

Answer 1

        DataRow[] dupresults = dt.Select("PROV_NEW");

The argument for dt.Select is a filter. "PROV_NEW" is not a valid filter as the expression doesn’t result to a boolean value. I believe you’re confusing this with SQL, where you can ask it to select a single column. But you don’t need to do that because later you need to select distinct off of the PROV_NEW column. If you want to make sure the whole row is distinct, then this is all you need to do.

If you only want compare the PROV_NEW column, you could write a custom equality comparer that looks at only your PROV_NEW column. You can reference your custom comparer when you call distinct with >this version <.

Alternatively Grant Winney suggested you could use Linq to select only the single column before using distinct. Refer to comments in their answer.