[Solved] Simplified Generics Grouping Helpers for Custom Binding

[Josh Anderson]

Requirements
RadControls version	2011.1.315
.NET version	4.0
Visual Studio version	VS 2010
programming language	C#
browser support	all browsers supported by RadControls

PROJECT DESCRIPTION
These helper methods utilize generics and reflection in order to simplify grouping when using custom binding. These are based on other examples provided by Telerik, but simplify usage by allowing you to avoid a series of if/then or switch statements based on the grouped field.  The helper class is as follows:

public static class TelerikGridHelpers
{
    public static IEnumerable<AggregateFunctionsGroup> BuildInnerGroup<T, TObject>(IEnumerable<TObject> group, Func<TObject, T> groupSelector, Func<IEnumerable<TObject>, IEnumerable> innerSelector)
    {
        return group.GroupBy(groupSelector)
                .Select(i => new AggregateFunctionsGroup
                {
                    Key = i.Key,
                    Items = innerSelector(i)
                });
    }

    public static Func<IEnumerable<TObject>, IEnumerable<AggregateFunctionsGroup>> BuildGroup<T, TObject>(Func<TObject, T> groupSelector, Func<IEnumerable<TObject>, IEnumerable<AggregateFunctionsGroup>> selectorBuilder)
    {
        var tempSelector = selectorBuilder;
        return g => g.GroupBy(groupSelector)
                     .Select(c => new AggregateFunctionsGroup
                     {
                         Key = c.Key,
                         HasSubgroups = true,
                         Items = tempSelector.Invoke(c).ToList()
                     });
    }

    public static IEnumerable<AggregateFunctionsGroup> ApplyGrouping<T>(IQueryable<T> data, IList<GroupDescriptor> groupDescriptors)
    {
        Func<IEnumerable<T>, IEnumerable<AggregateFunctionsGroup>> selector = null;
        foreach (var descriptor in groupDescriptors.Reverse())
        {
            var tempDescriptor = descriptor;
            if (selector == null)
                selector = g => BuildInnerGroup(g.Select(p => p), p => p.GetType().GetProperty(tempDescriptor.Member).GetValue(p, null), i => i.ToList());
            else
                selector = BuildGroup(p => p.GetType().GetProperty(tempDescriptor.Member).GetValue(p, null), selector);
        }

        return selector != null
                   ? selector.Invoke(data).ToList()
                   : null;
    }
}

In order to utilize these helpers in a custom binding scenario, you must first ensure that your data source first applies sorting by the fields (in reverse) in the GridCommand.GroupDescriptors argument to the controller action you're calling to get the GridModel.

Once you have your raw IEnumerable of the grid items, you simply need to return the GridModel as follows:

return command.GroupDescriptors.Any()
           ? new GridModel
                 {
                     Data = TelerikGridHelpers.ApplyGrouping(gridItems.AsQueryable(), command.GroupDescriptors),
                     // In my instance this is from my call to an NHibernate repository because I'm doing paging on the DB.
                     Total = (Int32) total.Value
                 }
           : new GridModel {Data = accountDTOs, Total = (Int32) total.Value};

This saves having to put "magic string" tests for the Member value of the group descriptor.

[Atanas Korchev]

Hi Josh Anderson,

Could you please provide a runnable example? You can check our code library guidelines for a reference.

Greetings,
Atanas Korchev
the Telerik team

[Luis]

Finally I got it!

With the help of the guys on this thread I'm proud to say that I came to a satisfactory result, pluggable in any type of MVC application without much difficulty and almost none in the settings.

I published the project on Bitbucket and Nuget, please take a look and send me some feedbacks.

https://bitbucket.org/Lunadie/telerikmvcgridcustombindinghelper/wiki/Home 

https://nuget.org/packages/TelerikMvcGridCustomBindingHelper