ToDataSourceResult loses Data

[Eric]

There must be something about the ToDataSourceResult method that I do not understand.  When DataSourceRequest.Page is 1, the resulting DataSourceResult.Data has the 10 elements that I passed into it, but, if DataSourceRequest.Page is 2, the resulting DataSourceResult.Data has 0 elements.  It is as if ToDataSourceResult is doing paging by only selecting the elements for the selected page range, but I am doing my own paging, so I want all elements passed to ToDataSourceResult to be included in DataSourceResult.Data.  Does this mean I should not be using ToDataSourceResult and should just populate the Data field manually?

 

request.Page = 1;
// results is a list of 10 elements
var gridModel = results.ToDataSourceResult(request);
// since Page is 1, dataCount will be 10
var dataCount = gridModel.Data.AsQueryable().Count();

request.Page = 2;
// results is a list of 10 elements
gridModel = results.ToDataSourceResult(request);
// since Page is 2, dataCount will be 0
dataCount = gridModel.Data.AsQueryable().Count();

[Anton Mironov]

Hello Eric,

Thank you for the provided details.

The ToDataSourceResult() method applies paging internally. Therefore, it would try to apply paging on the already paged data. What I can recommend is that you return a custom instance of the DataSourceResult class. Here is an example:

public ActionResult Remote_Binding_Orders_Read([DataSourceRequest]DataSourceRequest request)
        {
            //Apply custom paging to collection and pass it to the DataSource result object
            var result = new DataSourceResult()
            {
                Data = collection,
                Total = clientInput.Count()
            };

            return Json(result);
        }

A live demo demonstrating this functionality could be found here:

https://demos.telerik.com/aspnet-core/grid/customajaxbinding

Let me know if you need further assistance.

 

Regards,
Anton Mironov
Progress Telerik

[Frank]

@Anton Mironov

Hello, I hope this reaches you because my company bought your controls and they are great but I cannot seem to find an example of my exact needs.

I have an app with a grid, controller, and data and I am returning it as shown above but there is a requirement where a user on a different page will select a row and redirect to my page sending me a value to apply as a filter on a column as if it were done by the user.

When the view is returned, and the grid rendered, I want the column's filter icon to be lit up because of the filter I added.

I found this code snippet on another thread:

request.Filters.Add(new FilterDescriptor() { Member = "InsuredName", MemberType = typeof(string), Operator = FilterOperator.Contains, Value = "" });

but I cannot use this method if I am returning the data as shown above and not using ToDataSourceResult(request)

Thanks,

Frank

[Ivan Danchev]

Frank,

Review the following demo: https://demos.telerik.com/aspnet-mvc/grid/customajaxbinding In the demo's View Source tab you can see the server side logic, in particular the CustomAjaxBinding_Read action, in which filtering is applied to the data like this:

orders = orders.ApplyOrdersFiltering(request.Filters);

The ApplyOrdersFiltering method is declared at the end of the controller:

public static IQueryable<OrderViewModel> ApplyOrdersFiltering(this IQueryable<OrderViewModel> data,
           IList<IFilterDescriptor> filterDescriptors)
        {
            if (filterDescriptors != null && filterDescriptors.Any())
            {
                data = data.Where(ExpressionBuilder.Expression<OrderViewModel>(filterDescriptors, false));
            }
            return data;
        }

After applying filtering, sorting, paging, grouping, the orders collection is passed to the DataSourceResult() instance:

IEnumerable data =  orders.ApplyOrdersGrouping(request.Groups);

var result = new DataSourceResult()
{
    Data = data,
    Total = total
 };

return Json(result);

[Frank]

Thanks! This is very helpful.

-Frank

[Eric]

I am glad to hear that you have an example in the Core demos, but I am still using the original ASP.Net MVC 5 controls.  It would be nice if this was documented in those demos, as well.  I have not been looking at the Core demos, because I assumed the functionality would not be exactly the same.

[Anton Mironov]

Hi Eric,

It is correct that the same approach could be applied in the ASP.NET MVC framework. Based on the information in your first reply, I was not sure which framework was in use. Nevertheless, check out the corresponding live demo here:

https://demos.telerik.com/aspnet-mvc/grid

Let me know if there's anything else I can help you with.

Best Regards,
Anton Mironov
Progress Telerik