I am trying to implement a grid with a foreign key Column.
I am using your example
http://demos.telerik.com/aspnet-core/grid/foreignkeycolumn
I am trying to understand the right way to implement the editor template, unfortunately you didn't provide a full working example.
this is the error:
An unhandled exception occurred while processing the request.
ArgumentNullException: Value cannot be null.
Parameter name: items
.ctor
And this is the view
@(Html.Kendo().Grid<TraderMade.Models.Market>()
.Name("grid")
.Columns(columns =>
{
columns.Bound(c => c.Name).Width(200);
columns.ForeignKey(p => p.CountryId, (System.Collections.IEnumerable)ViewData["countries"], "Id", "Name")
.Title("Nazione").Width(150);
columns.Bound(c => c.City).Title("Città ").Width(150);
columns.Bound(c => c.MIC).Title("Codice").Width(80);
columns.Bound(c => c.WebSiteUrl).Title("Web site").Width(250);
columns.Command(command => command.Destroy()).Width(110);
})
.Filterable(ftb => ftb.Mode(GridFilterMode.Menu))
.HtmlAttributes(new { style = "height: 380px;" })
.ToolBar(toolbar =>
{
toolbar.Create();
toolbar.Save();
})
.Editable(editable => editable.Mode(GridEditMode.InCell))
.Scrollable()
.Groupable()
.Sortable()
.DataSource(dataSource => dataSource
.Ajax()
.Batch(true)
.ServerOperation(false)
.Events(events => events.Error("error_handler"))
.Model(model => model.Id(p => p.Id))
.Create("Countries_Create", "Home")
.Read("Countries_Read", "Home")
.Update("Countries_Update", "Home")
.Destroy("Countries_Delete", "Home")
).Deferred()
)
this is the relevant part of the controller
private void PopulateCountries()
{
var countries = _context.Countries.ToList();
ViewData["countries"] = countries;
ViewData["defaultCountry"] = countries.First();
}
public IActionResult Index()
{
PopulateCountries();
return View();
}
public ActionResult Countries_Read([DataSourceRequest] DataSourceRequest request)
{
var markets = _context.Markets;
DataSourceResult result = markets.ToDataSourceResult(request);
return Json(result);
}
I have read somewhere that I need to create a folder in views\shared\EditorTemplates, in this folder I have created
GridForeignKey.cshtml
@model object
@(
Html.Kendo().DropDownListFor(m => m)
.BindTo((SelectList)ViewData[ViewData.TemplateInfo.GetFullHtmlFieldName("") + "_Data"])
.ValuePrimitive(true)
)
here the model:
public class Country
{
public int Id { get; set; }
public string Name { get; set; }
public string CodeAlpha2 { get; set; }
public string CodeAlpha3 { get; set; }
public int CodeNumeric { get; set; }
public ICollection<Market> Markets { get; set; }
}
public class Market
{
public int Id { get; set; }
public string MIC { get; set; }
public string Code { get; set; }
public string Name { get; set; }
public string City { get; set; }
public string WebSiteUrl { get; set; }
public string Notes { get; set; }
public bool IsEnabled { get; set; }
public int CountryId { get; set; }
[ForeignKey("CountryId")]
public Country Country { get; set; }
}
I have tried to use ViewModel instead of model, but no matter what i write in columns.ForeignKey I have always the same error.
thank you for the support
3 Answers, 1 is accepted
The configuration seems correct and it is the same that is used in our online demo. You can also test the following example (which shows how to use a custom editor, but you can remove the EditorTemplateName and it should be the same as the demo):
On a side note, can you please elaborate if the error occurs when you try to open the cell for editing?
Looking forward to your reply.
Regards,
Konstantin Dikov
Telerik by Progress
Rank 1
Hello Konstantin,
I have tried, but I have the same error when I load the view
System.ArgumentNullException occurred
HResult=-2147467261
Message=Value cannot be null.
Parameter name: items
Source=Microsoft.AspNetCore.Mvc.ViewFeatures
ParamName=items
StackTrace:
at Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, String dataValueField, String dataTextField, IEnumerable selectedValues, String dataGroupField)
at Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, String dataValueField, String dataTextField, IEnumerable selectedValues)
at Microsoft.AspNetCore.Mvc.Rendering.SelectList..ctor(IEnumerable items, String dataValueField, String dataTextField, Object selectedValue)
at Microsoft.AspNetCore.Mvc.Rendering.SelectList..ctor(IEnumerable items, String dataValueField, String dataTextField)
at Kendo.Mvc.UI.Fluent.GridColumnFactory`1.ForeignKey[TValue](Expression`1 expression, IEnumerable data, String dataFieldValue, String dataFieldText)
at AspNetCore._Views_Home_About_cshtml.<ExecuteAsync>b__21_0(GridColumnFactory`1 columns) in /Views/Home/About.cshtml:line 13
InnerException:
I have followed your advice, but something strange happens with
ViewData["countries"] = countries.Select(e => new {
CountryId = e.Id,
Name = e.Name
});
If I look with the debug in the ViewData I have an exception
Results View = The type '<>f__AnonymousType0<CountryId,Name>' exists in both 'TraderMade.exe' and 'Microsoft.AspNetCore.Hosting.dll'
maybe my project.json have something wrong?
{
"dependencies": {
"Microsoft.AspNetCore.Diagnostics": "1.0.0",
"Microsoft.AspNetCore.Mvc": "1.0.1",
"Microsoft.AspNetCore.Razor.Tools": {
"version": "1.0.0-preview2-final",
"type": "build"
},
"Microsoft.AspNetCore.Routing": "1.0.1",
"Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
"Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
"Microsoft.AspNetCore.StaticFiles": "1.0.0",
"Microsoft.EntityFrameworkCore": "1.0.1",
"Microsoft.EntityFrameworkCore.SqlServer": "1.0.1",
"Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
"Microsoft.Extensions.Configuration.Json": "1.0.0",
"Microsoft.Extensions.Logging": "1.0.0",
"Microsoft.Extensions.Logging.Console": "1.0.0",
"Microsoft.Extensions.Logging.Debug": "1.0.0",
"Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
"Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0",
"Microsoft.EntityFrameworkCore.Tools": {
"version": "1.0.0-preview2-final",
"type": "build"
},
"Telerik.UI.for.AspNet.Core": "2016.3.1118"
},
"tools": {
"Microsoft.EntityFrameworkCore.Tools": {
"version": "1.0.0-preview2-final",
"imports": [
"portable-net45+win8+dnxcore50",
"portable-net45+win8"
]
},
"BundlerMinifier.Core": "2.0.238",
"Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final",
"Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final"
},
"frameworks": {
"net461": {
}
},
"buildOptions": {
"emitEntryPoint": true,
"preserveCompilationContext": true
},
"publishOptions": {
"include": [
"wwwroot",
"**/*.cshtml",
"appsettings.json",
"web.config"
]
},
"scripts": {
"prepublish": [ "bower install", "dotnet bundle" ],
"postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
}
}
thank you
renato
The stack trace of the error indicates that the collection that you are passing is null. Can you please ensure that the values are correctly set in the ViewData:
public ActionResult Index() { PopulateCountries(); return View(); }private void PopulateCountries() { var countries = _context.Countries.ToList(); ViewData["countries"] = countries; //the error will be thrown if contries is null ViewData["defaultCountry"] = countries.First(); }You can also try the following:
ViewData["countries"] = _context.Countries;Regards,
Konstantin Dikov
Telerik by Progress