[Solved] Receiving metadata

[cp]

Hello,
Is it possible to receive metadata in the onDataBound event handler, just like one can send metadata in the OnDataBinding handler?

I have this case where we use CustomBinding, however I need to return some additional data on top of the collection that gets bound to the grid.

[GridAction(EnableCustomBinding = true)]
        public ActionResult GetNewPage(...)
        {
            [...]
            return View(new GridModel
            {
                Data = ApplyPaging(data, command.Page, command.PageSize),
                Total = data.AsQueryable().Count()
            });
        }

Thanks,

[Daniel]

Hello Claudiu,

Sending additional data is not supported out of the box and will require some additional code. Basically, you should inherit the GridActionAttribute and override the OnActionExecuted and the CreateActionResult methods. The additional data can be obtained on the client from the event argument's response property of the OnComplete client-side event e.g.

public class MyGridActionAttribute: GridActionAttribute
{
    private ActionExecutedContext context;
    //Add the ActionExecutedContext to the attribute in order to get access to the
    // Controller context
    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        this.context = filterContext;
        base.OnActionExecuted(filterContext);
    }

    // Add the additional data from the ViewData/ViewBag to the result
    protected override ActionResult CreateActionResult(object model)
    {
        var dictionary = model as Dictionary<string,object>;
        var data = context.Controller.ViewData["additionalData"];
        dictionary.Add("additionalData", data);
        return base.CreateActionResult(model);
    }
}

Kind regards,
Daniel
the Telerik team

[Alexander]

Hi Daniel,

Thanks for the solution. Unfortunately it's not thread safe. Current context field could be overwritten before CreateActionResult is called. I wonder if it's possible to send additional data in a safe way.

Thanks,
Alexander

[Daniel]

Hello Alexander,

I am not sure if I understand correctly in which case the context would be overwritten since there are no static members and the Controller is created for each request. Could you provide a sample scenario in which the problem could occur?

Regards,
Daniel
the Telerik team

[Alexander]

Hi Daniel,

Yes, Controller is created for each request, but GridActionAttribute is not (as far as I understand).

So, when Thread 1 enters OnActionExecuted method, a reference to the current context is stored to a field and base.OnActionExecuted is executed. The base method does some stuff and calls virtual method CreateActionResult where previously stored context is used. If a processor switches to another thread (Thread 2) before CreateActionResult is called on Thread 1 and executes OnActionExecuted on Thread 2, the reference to the context of Thread 1 is rewritten with a context of Thread 2. Thus, both ActionResults have the same additionalData, because both of the threads have the same context.

Please let me know if it's still unclear. I'm really interested in a good solution. Right now I'm using System.Web.HttpContext.Current.Items to pass the data from a controller to a GridActionAttribute, but I wonder if it's possible to get rid of static HttpContext.Current.

Thanks,
Alexander

[Daniel]

Hello again Alexander,

I apologize for missing that the attribute is not created for each request. I am afraid that currently there isn't another way to pass the extra data. An option is to write your own version of the OnActionExecuted method which uses similar code as the GridActionAttribute and supports passing the needed data.

Regards,
Daniel
the Telerik team