Question

I’m learning Linq and MVC2 I’m making progress, but I’m a little stuck on how I should get a page descrption into a View that uses a collection.

In my controller I have the following construct

public ActionResult Group(int id)
{
    var result = (from d in db.ErrorDetails.Where(r => r.ErrorTerminal.ErrorTerminalGroupID == id)
                  orderby d.ErrorTerminal.TerminalNumber ascending, d.ErrorRecordedAt descending
             select d);

    return View(result);
}

and on my view

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2>????? how to get a title from the 1st record?????</h2>
<table>
<%
        foreach (var item in Model) {
%>
//code for setup of the rows etc
<% }%>
</table>

How do I get the Title from the Linq query that I made, OR do I need to make a ViewModel to house that?

Answer 1

Please do not pass IEnumerable<T>s to your view. Instead consider using a List<T> and do the first-time enumeration in the controller. I only recommend this pattern for ViewModels because you can catch the exception of the first-time enumeration in your controller code and not let the view rendering die horribly and result in partial HTML output because the controller screwed up and passed the view something it could not fully enumerate over.

That being said, the best approach is to use a ViewModel and have it house properties string Title and List<ErrorDetail> ErrorDetails.

public class GroupErrorDetailsViewModel
{
    public string Title { get; set; }
    // NOTE: assuming db.ErrorDetails is of type Table<ErrorDetail>
    public List<ErrorDetail> ErrorDetails { get; set; }
}

public ActionResult Group(int id)
{
    // FIXME: this direct database query should not really be in the controller
    var result =
        from d in db.ErrorDetails
        where d.ErrorTerminal.ErrorTerminalGroupID == id
        orderby d.ErrorTerminal.TerminalNumber ascending, d.ErrorRecordedAt descending
        select d;

    var resultList = result.ToList();

    var viewModel = new GroupErrorDetailsViewModel
    {
        Title = resultList.Count > 0 ? resultList[0].Title : "Default Title",
        ErrorDetails = resultList
    };

    return View((object)viewModel);
}