"Cannot Resolve Symbol Select" Trying to use LINQ with DataRowCollection

Question

I'm trying to use LINQ to iterate over the rows in a DataTable, and instantiate objects from the column values. The tricksy code is shown below.

The problem is that the code won't even compile. The nefarious error message is "cannot resolve symbol Select".

I'm satisfied that DataRowCollection implements IEnumerable (it gets it from System.Data.InternalDataCollectionBase), so you would think there'd be no problem with the following (obviously, I'm wrong on that count).

I have included System.Linq System.Data, and System.Data.SqlClient in my project. It also has all the necessary references. I've been using LINQ throughout the app before (mostly with lists of POCOs and XDocuemnts), and this is the first time I've seen this particular message.

Any advice on how to resolve it?

using (var command = connection.CreateCommand())
{
    command.CommandText = "dbo.sp_pTicklerContacts_sel_W_ContactRole_by_ComKey";
    command.CommandTimeout = 120;
    command.CommandType = CommandType.StoredProcedure;
    command.Parameters.Add("@iComKey", SqlDbType.Int).Value = companyKey;

    using (var adapter = new SqlDataAdapter(command))
    {
        var dataset = new DataSet();
        adapter.Fill(dataset);
        if (dataset.TableCount() > 0 && dataset.Tables[0].Rows.Count > 0)
        {
            return (from row in dataset.Tables[0].Rows
                    select new TicklerContact
                               {
                                   CompanyKey = row.ToInt32("iTicklerContact"),
                                   Contact = row.ToString("ccontact"),
                                   ContactKey = row.ToInt32("iconkey"),
                                   TicklerContactKey = row.ToInt32("iTicklerContactKey"),
                                   Role = row.ToString("contactrole"),
                                   Exists = row.ToBool("contactexists")
                                 }).ToList();

        }
        return null;
    }
}

Do you get a line highlighted with the error message? – Tony Abrams Jan 12 '11 at 18:45 — Tony Abrams, Jan 12 '11 at 18:45

score 7 · Accepted Answer · edited May 23 '17 at 12:09

7

I don't think you can use Linq over DataSet rows since it doesn't implement IEnumerable<T>. If you add a reference to System.Data.DataSetExtensions to your project you can use an extension method though, that allows you this:

 return (from row in dataset.Tables[0].AsEnumerable()
 ...

Also see this previous answer on SO: LINQ query on a DataTable

From the msdn article for DataTableExtensions.AsEnumerable:

Language-Integrated Query (LINQ) queries work on data sources that implement the IEnumerable interface or the IQueryable interface. The DataTable class does not implement either interface, so you must call the AsEnumerable method to use the DataTable as a source in the From clause of a LINQ query. You can also obtain custom, domain-specific operators, such as CopyToDataTable, by returning an IEnumerable object.

edited May 23 '17 at 12:09

Community

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answered Jan 12 '11 at 18:45

BrokenGlass

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That's odd considering you can use linq against a DataRowCollection in VB. – Tony Abrams Jan 12 '11 at 18:49
BTW, DataRowCollection inherits from InternalDataCollectionBase which implements IEnumerable, so I would think it works fine with LINQ. – Tony Abrams Jan 12 '11 at 19:01
@Tony: I looked at your approach and that will work as well, as you did you have to specify the type of the range variable since the IEnumerable collection from the DataRowCollection is untyped - this would not have been neccessary if DataRowCollection implemented IEnumerable – BrokenGlass Jan 12 '11 at 19:12
you have to love the little things :P – Tony Abrams Jan 12 '11 at 19:42

Tony Abrams · Answer 2 · 2011-01-12T18:52:05.960

Maybe you need to help LINQ out on this one. It cannot resolve the type of row?

Try:

return (from row as DataRow in dataset.Tables[0].Rows
                select new TicklerContact
                           {
                               CompanyKey = row.ToInt32("iTicklerContact"),
                               Contact = row.ToString("ccontact"),
                               ContactKey = row.ToInt32("iconkey"),
                               TicklerContactKey = row.ToInt32("iTicklerContactKey"),
                               Role = row.ToString("contactrole"),
                               Exists = row.ToBool("contactexists")
                             }).ToList();

EDIT

Stupid VB / C# brain smash :P

Try:

return (from DataRow row in dataset.Tables[0].Rows
                select new TicklerContact
                           {
                               CompanyKey = row.ToInt32("iTicklerContact"),
                               Contact = row.ToString("ccontact"),
                               ContactKey = row.ToInt32("iconkey"),
                               TicklerContactKey = row.ToInt32("iTicklerContactKey"),
                               Role = row.ToString("contactrole"),
                               Exists = row.ToBool("contactexists")
                             }).ToList();

Nope, no go. But it was a promising suggestion! – Mike Hofer Jan 12 '11 at 18:43 — Mike Hofer, Jan 12 '11 at 18:43

"Cannot Resolve Symbol Select" Trying to use LINQ with DataRowCollection

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