Sql – Which fields will be queried when using LINQ to SQL bind to a gridview

There isn't direct support for COUNT(DISTINCT {x})), but you can simulate it from an IGrouping<,> (i.e. what group by returns); I'm afraid I only "do" C#, so you'll have to translate to VB...

 select new
 {
     Foo= grp.Key,
     Bar= grp.Select(x => x.SomeField).Distinct().Count()
 };

Here's a Northwind example:

    using(var ctx = new DataClasses1DataContext())
    {
        ctx.Log = Console.Out; // log TSQL to console
        var qry = from cust in ctx.Customers
                  where cust.CustomerID != ""
                  group cust by cust.Country
                  into grp
                  select new
                  {
                      Country = grp.Key,
                      Count = grp.Select(x => x.City).Distinct().Count()
                  };

        foreach(var row in qry.OrderBy(x=>x.Country))
        {
            Console.WriteLine("{0}: {1}", row.Country, row.Count);
        }
    }

The TSQL isn't quite what we'd like, but it does the job:

SELECT [t1].[Country], (
    SELECT COUNT(*)
    FROM (
        SELECT DISTINCT [t2].[City]
        FROM [dbo].[Customers] AS [t2]
        WHERE ((([t1].[Country] IS NULL) AND ([t2].[Country] IS NULL)) OR (([t1]
.[Country] IS NOT NULL) AND ([t2].[Country] IS NOT NULL) AND ([t1].[Country] = [
t2].[Country]))) AND ([t2].[CustomerID] <> @p0)
        ) AS [t3]
    ) AS [Count]
FROM (
    SELECT [t0].[Country]
    FROM [dbo].[Customers] AS [t0]
    WHERE [t0].[CustomerID] <> @p0
    GROUP BY [t0].[Country]
    ) AS [t1]
-- @p0: Input NVarChar (Size = 0; Prec = 0; Scale = 0) []
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 3.5.30729.1

The results, however, are correct- verifyable by running it manually:

        const string sql = @"
SELECT c.Country, COUNT(DISTINCT c.City) AS [Count]
FROM Customers c
WHERE c.CustomerID != ''
GROUP BY c.Country
ORDER BY c.Country";
        var qry2 = ctx.ExecuteQuery<QueryResult>(sql);
        foreach(var row in qry2)
        {
            Console.WriteLine("{0}: {1}", row.Country, row.Count);
        }

With definition:

class QueryResult
{
    public string Country { get; set; }
    public int Count { get; set; }
}

You should not have to convert to a List or Array. Binding requires, at a minimum, an IEnumerable<T>, which is what your Users variable is. Anonymous types are simply pre-compile place holders for compiler generated concrete types, so you should also be able to bind to anonymous types.

Your GridView may not have the AutoGeneratedColumns property set, which is what is required to have the data source define what columns appear. Try enabling that, and see if your GridView displays your queries results.