Problem with grid when trying to use groupby in LINQ

When trying to use GROUPBY I get an error saying a field 'date1' is not found on selected resource.

   var query = (from a in db.Dates
                     from b in db.Facts

                     where a.Count_Key == b.Date_key

                         select new{
                             a.Date1,
                           a.Month,
              开发者_运维知识库           b.Fact_key
                         });
        var query2 = query.GroupBy(x =>  x.Month );
        Grid1.DataSource = query2;
        Grid1.DataBind();

So, when I try to bind with query it works perfectly, but query2 yields the error

field date1 not found on selected datasource.

How can I fix this?

---

The group by returns columns with different names than the original select.

You can do the following to see it "for educational purpose".

create a new Grid2 and use it with automatic columnmapping. Bind Query2 to this Grid2 and you will see the result.

---

Because you grouped by month, now you have only month field as a key, and collection of grouped items. If you want more fields on data source you need to use aggregate function on date1 field.

For example like this:

var query2 = (from q in query
             group q by q.Month into g
             select new 
                       {
                          Month = g.Key,
                          Date = g.Select(gg=>gg.Date1).Max //or you can use first here etc.
                       }).ToList()

hope this helps