First attempt at a Grid; Fail

[IPV]

Model

public class Switch
{
    [DisplayName("Switch Id")]
    public string SwitchId { get; set; }
}

Controller

public class UserConsoleViewModelsController : Controller
{
    public ActionResult FilteredSwitches_Read([DataSourceRequest]DataSourceRequest request)
    {
        var filteredSwitches = GetFilteredSwitches().ToDataSourceResult(request);  //3 records are here at runtime
        return Json(filteredSwitches);
    }

    private IEnumerable<Switch> GetFilteredSwitches()
    {
        return db.Switches.ToList();
    }
}

View

@(Html.Kendo().Grid<Switch>()
    .Name("grid")
    .Columns(columns =>
    {
        columns.Bound(c => c.SwitchId).Width(140);
    })
    .HtmlAttributes(new { style = "height: 380px;" })
    .Scrollable()
    .Groupable()
    .Sortable()
    .Pageable(pageable => pageable
        .Refresh(true)
        .PageSizes(true)
        .ButtonCount(5))
    .DataSource(dataSource => dataSource
        .Ajax()
        .Read(read => read.Action("FilteredSwitches_Read", "UserConsoleViewModels"))
    )

I get a grid, but there are no rows in it for the 3 records known to be in 'FilteredSwitches_Read()'.

What am I doing wrong?

Dave

[Dimiter Madjarov]

Hello Dave,


The sample code looks correct. I would suggest you to check the developer tools console for JavaScript errors and also the network tab to assure that the request to the FilteredSwitches_Read action was successful.

I am looking forward to hearing from you.

Regards,
Dimiter Madjarov
Telerik

 

 

[IPV]

There was an error indicated in the dev tools...  apparently there was something about my model that the Json-ifier didn't like. Thinking I was using the control incorrectly, I presented a simplified version of my model in my first post.  I am now using that simplified model and it is working.  Now to slowly work toward the more complex model until I find the issue.

Thank you!

[Dimiter Madjarov]

Hello Dave,


Probably the reason was a circular reference. If that is the case you should extract a ViewModel containing only the needed properties. More information is available in the documentation.

Regards,
Dimiter Madjarov
Telerik

 

 

[IPV]

Yes, a Circular Reference was indeed the error and indeed I did solve it with a less complex view model.  Now I have another issue. Please let me know if I should post this as a new question.

My ViewModel looks like this.

public class UserConsoleSwitchGridModel

{

    public string SwitchId { get; set; }

    public string SentinelId { get; set; }

    public DateTime MostRecentNormal

    {

        get

        {

            var db = new ApplicationDbContext();

            try

            {

                var throws = db.SwitchThrows

                    .Where(s => s.SwitchId == SwitchId)

                    .Where(a => a.Action == "Normal")

                    .OrderByDescending(t => t.Timestamp)

                    .Take(1);

 

                var _throw = throws.ToList().ElementAt(0);               

                return _throw.Timestamp;

 

            }

            catch

            {

                return DateTime.MinValue;

            }

        }

    }

    [DisplayName("Most Recent Reverse Throw")]

    public DateTime MostRecentReverse

    {

        get

        {

            {

                var db = new ApplicationDbContext();

                try

                {

                    var throws = db.SwitchThrows

                        .Where(s => s.SwitchId == SwitchId)

                        .Where(a => a.Action == "Reverse")

                        .OrderByDescending(t => t.Timestamp)

                        .Take(1);

 

                    var _throw = throws.ToList().ElementAt(0);                   

                    return _throw.Timestamp;

                }

                catch

                {

                    return DateTime.MinValue;

                }

            }

        }

    }

}

Controller

public ActionResult FilteredSwitches_Read([DataSourceRequest]DataSourceRequest request)
{
    var filteredSwitches = GetFilteredSwitches().ToDataSourceResult(request);
    return Json(filteredSwitches);
}

private IEnumerable<UserConsoleGridModel> GetFilteredSwitches()
{
    var userid = User.Identity.GetUserId();
    var user = db.Users.First(u => u.Id == userid);
    return
        db.Switches.Include(i => i.Sentinel).Include(n => n.MostRecentNormalSwitchThrow).Include(r => r.MostRecentReverseSwitchThrow)
            .Where(c => c.CompanyId == user.Company.CompanyId)
            .Select(x => new UserConsoleGridModel()
            {
                SwitchId = x.SwitchId,
                SentinelId = x.SentinelId
            });
}

@(Html.Kendo().Grid<UserConsoleGridModel>()
    .Name("grid")
    .Columns(columns =>
    {
        columns.Bound(c => c.SwitchId).Width(140);
        columns.Bound(c => c.SentinelId);
        columns.Bound(c => c.MostRecentNormal);
        columns.Bound(c => c.MostRecentReverse);
    })
    .HtmlAttributes(new { style = "height: 380px;" })
    .Scrollable()
    .Groupable()
    .Sortable()
    .Pageable(pageable => pageable
        .Refresh(true)
        .PageSizes(true)
        .ButtonCount(5))
    .DataSource(dataSource => dataSource
        .Ajax()
        .Read(read => read.Action("FilteredSwitches_Read", "UserConsoleViewModels"))
    )
)

This works fine on first render, on refresh, of if I sort on either of the two string 'Id' columns, but if I sort on either of the DateTime columns I get this error:

The specified type member 'MostRecentReverse' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

How do you suggest I do this?  Please know that the value of either/both the two DateTime fields could change between sorts.

Thanks!

[Dimiter Madjarov]

Hello Dave,


The current problem does not seem directly related to Kendo UI, but to the way the data is retrieved. I found similar forum threads (for example here and here), that could help in resolving it.

Regards,
Dimiter Madjarov
Telerik