How to sort DataTable by 2 columns, with NULLs, maybe using LINQ?

Question

I have an ADO.Net datatable that I need to sort by first by column1 then by column2, either of which may have nulls. Once sorted I need to read some values out of the rows and add to a listview.

I have written code to do this DataTable.DefaultView.Sort (run twice). But wondering if there might be a better way.

I was thinking maybe LINQ...so I tried :

OrderedEnumerableRowCollection<DataRow> queryX = dt.AsEnumerable()
            .OrderBy(c => c.Field<int?>("column1"))
            .ThenBy(c => c.Field<int?>("column2"));

But this errors with "System.InvalidCastException was unhandled". I assumed this is caused by the NULLs so just as a test I specifying a query on the datatable "where column1 IS NOT NULL" and the error still happens.

I don't really have much LINQ experience so my questions are:

• What is incorrect with my code above? Conceptually I'm I missing something on how LINQ works?
• Why does filtering out the Nulls still cause this? Again, conceptually I'm I missing something on how LINQ works
• Is there a better\correct LINQ query that would to this?
• Is there a better\correct (more elegant) way to do this (using LINQ or not)?

tep

Answer 1

If you have a DataTable, take a look at DataView:

private void SortByTwoColumns()
{
    // Get the DefaultViewManager of a DataTable.
    DataView view = DataTable1.DefaultView;

    // By default, the first column sorted ascending.
    view.Sort = "State, ZipCode DESC";
}

Source: http://msdn.microsoft.com/en-us/library/system.data.dataview.sort.aspx