Joined Linq query to DataTable and result to DataView

Question

I have two DataTables , Items and its Groups. I have a linq query to get item Name and its Group Name by joining the 2 tables.

    EnumerableRowCollection<DataRow> dvquery = (from item in Items.AsEnumerable()
                                                            join grp in groups.AsEnumerable()
                                                              on item.Field<byte>("Group_ID") equals grp.Field<byte>("ID")
                                                              into item_grp_join
                                                              from itemgrp in item_grp_join
                                                              select new
                                                              {
                                                                  ItemName = (string)led.Field<string>("Name"),
                                                                  GName = (string)itemgrp.Field<string>("Name"),
                                                              });

            DataView dv = dvquery.AsDataView();

However I am getting compile time error as

Cannot implicitly convert type 'System.Collections.Generic.IEnumerable' to 'System.Data.EnumerableRowCollection'. An explicity conversion exists (are you missing a cast?)

How to solve this error? I can easily convert the query result into a list but I need to have a dataview only , so as I can give it as datasource to grid.

Any help appreciated. Thanks

This LINQ query returs an IEnumerable and if you want it to return a EnumerableRowCollection that you can simply do .AsDataView() then you just need to do e SELECT item (the whole object not an anonymous type). Hope this helps someone else — kuklei, Apr 10 '20 at 22:05

score 4 · Answer 1 · edited Mar 28 '12 at 08:21

The problem is that your query returns an IEnumerable<T> of an anonymous type and you can't simply cast that to a EnumerableRowCollection<DataRow>

I'm now sure which type of Grid you are using (e.g. from winforms? WPF? ASP? ASP MVC? etc), however I would expect that you should actually be able to pass it the IEnumerable output of the linq query if you wanted to - e.g.:

var query = (from item in Items.AsEnumerable()
             join grp in groups.AsEnumerable()
             on item.Field<byte>("Group_ID") equals grp.Field<byte>("ID")
             into item_grp_join
             from itemgrp in item_grp_join
             select new
             {
                ItemName = (string)led.Field<string>("Name"),
                GName = (string)itemgrp.Field<string>("Name"),
             });
grid.DataSource = query; // or possible query.ToList() as you suggest in the question!

If you really need to use a DataView type object, then there are blog posts about how to create these, try:

Note that if you are expecting to use the grid for two-way binding (e.g. for writing changes back to the database), then this is unlikely to "just work" - as your IEnumerable projection isn't tied back to the datasource.

All the above references you mentioned first convert the query into datatable and then dataview on datatable can be set. I think then this is only option left. What if I set dataview on Datatable which was generated by Linq query ,and then somehow DataTable gets destroyed. Will the DataView work then? — Hakim, Sep 09 '11 at 09:29

score 2 · Answer 2 · answered Sep 08 '11 at 13:04

You are returning an list of anonymous objects. It is better to create a DataTable from your query result.

var query = (from item in Items.AsEnumerable() .......

 DataTable view = new DataTable();
 view.Columns.Add("GroupName");
 view.Columns.Add("ItemName");
 foreach (var t in dvquery)
       {
        view.Rows.Add(t.GName, t.ItemName);
       }
 DataView dv = view.DefaultView;

Joined Linq query to DataTable and result to DataView

2 Answers2