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First attempt at a Grid; Fail

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Grid
This is a migrated thread and some comments may be shown as answers.
IPV
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IPV asked on 27 Nov 2014, 06:16 PM
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

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Dimiter Madjarov
Telerik team
answered on 28 Nov 2014, 11:41 AM
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
 

Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.

 
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IPV
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answered on 28 Nov 2014, 04:32 PM
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!
0
Dimiter Madjarov
Telerik team
answered on 28 Nov 2014, 04:40 PM
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
 

Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.

 
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IPV
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answered on 29 Nov 2014, 05:27 AM
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!
0
Accepted
Dimiter Madjarov
Telerik team
answered on 01 Dec 2014, 09:38 AM
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
 

Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.

 
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Dimiter Madjarov
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