I'm using a Listview to display some data using model binding and I'm trying to sort a column in the listview that relates to a foreign key column in the data source, namely the book column.
The Data Model is as follows:
public class Book
{
public Book() {
this.Factions = new HashSet<Faction>();
}
public int Id { get; set; }
[Required]
[MaxLength(50)]
public string Title { get; set; }
public virtual ICollection<Faction> Factions { get; set; }
}
public class Faction
{
public int Id { get; set; }
[Required]
[MaxLength(50)]
public string Name { get; set; }
[MaxLength(10)]
public string Abbreviation { get; set; }
public int? BookId { get; set; }
public virtual Book Book { get; set; }
}
And this is the HTML to display the headings for the ListItem
<asp:ListView ID="FactionListView" runat="server"
ItemType="DCW.Models.Faction" DataKeyNames="Id"
SelectMethod="FactionGetData"
<LayoutTemplate>
<table class="table table-hover table-bordered">
<thead>
<tr>
<th>
<asp:LinkButton ID="FactionListViewName" runat="server" CommandName="Sort"
CommandArgument="Name">Name</asp:LinkButton></th>
<th>
<asp:LinkButton ID="FactionListViewAbbreviation" runat="server" CommandName="Sort"
CommandArgument="Abbreviation">Abbreviation</asp:LinkButton></th>
<th>
<asp:LinkButton ID="FactionListViewBook" runat="server" CommandName="Sort"
CommandArgument="Book">Book</asp:LinkButton></th>
</tr>
</thead>
<tbody>
<asp:PlaceHolder ID="itemPlaceholder" runat="server" />
</tbody>
</table>
</LayoutTemplate>
When clicking on the Book LinkButton I get the error: Sys.WebForms.PageRequestManagerServerErrorException: DbSortClause expressions must have a type that is order comparable.
If I change the Linkbutton CommandArgument to either Book.Id or it.Book.Title (which I had read on some other posts might work) then I get the error: Sys.WebForms.PageRequestManagerServerErrorException: Exception has been thrown by the target of an invocation.
So how do I sort a related column of a Model Bound Listview?
Thanks.
So it seems that Model Binding doesn't handle sorting Navigation Properties (Foreign Keys) out of the box. I found the following which is what I used to solve this problem: ASP.Net 4.5 Model Binding Sorting By Navigation Property
So this:
<asp:LinkButton ID="FactionListViewBook" runat="server" CommandName="Sort"
CommandArgument="Book">Book</asp:LinkButton></th>
Became:
<asp:LinkButton ID="FactionListViewBook" runat="server" CommandName="Sort"
CommandArgument="Book.Title">Book</asp:LinkButton></th>
And my SelectMethod became:
public IQueryable<GameFaction> FactionGetData(string sortByExpression)
{
IQueryable<Faction> query = _context.Factions.Include(faction => faction.Book);
sortByExpression = sortByExpression == null ? "Name" : sortByExpression;
if (sortByExpression.EndsWith(" DESC"))
{
query = query.OrderByDescending(sortByExpression.SubString(0, sortByExpression.Length - 5));
}
else
{
query = query.OrderBy(sortByExpression);
}
return query;
}
Note that this uses the extension method mentioned in the link above which originally came from here: Dynamic LINQ OrderBy on IEnumerable<T>