Passing Gridview Paging/Sorting/Grouping/Filtering expressions to business logic Select Methods

Hi Nabeel,
Thank you for the detailed description of the problem.
I understand the functionality you wish to achieve, but I'm afraid there is no easy way to do the same thing when working with ASPxGridView. Please look at the following report to learn more on this subject:
ID: Q100566, Sort the grid at database level!
So, the only thing we can suggest is to implement the IListServer interface at your datasource level, as suggested in this report (please note, this is not an easy task) or work with the grid in Server mode. Please look at the following help topics to learn more:
Server-side Data Management
LINQ Server Mode
However, in this instance, you'll have to substitute your ObjectDataSource with either LINQServerModeDataSource or XpoDataSource.
Thanks,
Vito

Hi Vito,
Thanks for the quick response. I have gone through all the info and suggested article you provided and I am a bit confused.
I don't understand why a basic feature that was already there in the ASP.NET Gridview/ObjectDatasOurce is not available in your advance gridview. Why can you not just add this feature to your grid, so that the pagesize, rowindex, filter and grouping expression can be passed to the business objects method via object datassource in some form of string or predefined xml format or something.
I have been evaluating Obout Grid and they provide the same simple method of passing all the parameters via object datasource in a propreity string format, whch can easily be parsed to build a sql query. Infact they got two modes, client side and server side. In server mode all the sorting/paging/groupin/filtering can be done at database level manually via string expressions passed through the grid/ & objectdatasource. Can you not provide the same feature. That would be fantastic. You mentioned "claculation of group and summaries", we can do that at database level by ourselve as well. Just provide us the expressions. Also, just like we write "SelectCount" method to aid paging with objectdatasource we can also write a couple of more methods for calculating group and summaries based on if it is required or not :)
I read about IListServer implementationa and it seems too complicated. I also read and watch the webcasts of XPO and LinqServerModeDataSource by Mahul and the preference of LinkServerModeDataSource over XPO. but then again its all done by creating a separate DataAccess layer (the .dbml file or object persistence classes) with data tables. What about my Business Objects and their methods? I would like to bind my business objects to the grid instead of the dbml tables. Is there a way to do it?
Also the linqservermodedatasource TableName property allows it to point to one table only. My Select queries involve complex joins. How would i achieve that.
All this seems like a whole new learning curve and contradict the whole point. I was expecting to replace the existing UI in our systems with some rich UI and some extra functionality without the need of binning or rewriting our business logic and dataaccess layers.
I have also notice that the Grid keeps binding itself everytime there is a postback even via a button click outside the grid that has got nothing to do with the grid at all. Doesn't make any sense? it keeps calling stored procedures, wasting processing time and memory on the server? Is this the normal behavior? Is there a way to disable it or somehow cancel the binding when it is not required ? I understand that it needs to rebind when clicked for paging/sorting/grouping but why it does that for a button click that is not defined in the grid and has got nothing to do with the grid at all?
Awaiting
Nabeel

Forgot to mention that the implementation of IListServer at http://www.devexpress.com/Support/Center/e/E166.aspx only supports paging and does not support filtering, grouing and summary either. So does that mean if i want to have database level paging along with filtering, grouping… I have only got linqservermodedatasource option?

Just read in the documentation that the DataSourceForceStandardPaging property of aspxgridview enables the capability to pass default data source paging parameters to the ExecuteSelect(). So I assume this means there is no need of implementing IListServer interface if only paging and sorting is to be done on database level? But to have the grouping,filtering and summary calculation along with paging, IListServer implementaiton of the datasource is required (e.g. LinkServerModeDataSource). Please correct me if I am wrong? And also how would I use LinkServerModeDataSource with my business objects?
Awaiting
Nabeel Farid

Hi guys
Could you please answer my following queries:

1. Is it possible to achieve database level Paging, Sorting, Filtering, Grouping by implementing the IListServer Interface?
2. Is it possible to achieve database level Paging, Sorting, Filtering, Grouping by using DataSourceForceStandardPaging?
3. Why the grid can not pass the Standard Paging Parameters, Filter Expression, Grouping Expression, Sort Expression in some predefined format to the business object methods, so that it can be parsed and all the functions can be performed at database level?
4. Can we use LinqServerModeDataSource with custom business objects instead of using dbml file classes?
5. Can we perform complex joins (inner/outer) with LinqServerModeDataSource?
6. My goal was to replace the standard ASP.NET UI control in our existing applications with DevX. But if I have to rewrite the business and data access logic using dbml files, it does not make any sense?
   Awaiting
   Nabeel Farid

Hi Nabeel,
Indeed, the DataSourceForceStandardPaging property is the thing that you should use in your application if you need only server side paging and sorting. If you also need to support grouping, filtering, summary you need to support the IListServer interface in your DataSource class.
>>
And also how would I use LinkServerModeDataSource with my business objects?
<<
This depends upon your business objects and it is difficult to answer your questions not having your code.
Here are answers to your questions:

1. Yes.
2. No. In this mode, only paging and sorting work.
3. This is done through IListServer interface members.
4. dbml files contain data in the database markup language and are used for the LinqToSQL provider only. However, Linq can be used to fetch data using other providers. Generally, the LinqServerModeDataSource can accept any Linq query in the Selecting event and then fetch data from the data store. Sorry, I do not know the specifics of your objects and thus it is rather difficult to answer your question.
   4:-) The LinqServerM odeDataSource provides the Selecting event which can be used to pass a custom queryable object. It can be used to fetch data from the underlying data store.
5. It depends upon numerous factors. We cannot help you make a decision here. Perhaps, you are right and there is no need to invest a lot of time in changing the UI.
   Thanks,
   Plato

Hi Nabeel:
We're working on this issue and will answer you as soon as possible. Please accept our apologies for the delay.
Thanks
Kate.

Thanks for the reply Plato. I have got few more queries.

1. In your last reply you said that by using DataSourceForceStandardPaging=True with objectdatasource, both Paging and Sorting can be perform at database level. I know how to do paging but I was wondering how to perform sorting. Does the objectdatasiyrce provide the Sort expression as well like PageSize and StartRowIndex?
2. I have noticed that the AspxGridView keeps binding itself everytime there is a postback even via a button click outside the grid that has got nothing to do with the grid at all. Doesn't make any sense? it keeps calling stored procedures, wasting processing time and memory on the server? Is this the normal behavior? Is there a way to disable it or somehow cancel the binding when it is not required ? I understand that it needs to rebind when clicked for paging/sorting/grouping but why it does that for a button click that is not defined in the grid and has got nothing to do with the grid at all?
   Awaiting
   Nabeel

Hi Nabeel,

1. The information about sorting is passed to the Select method of the ObjectDataSource via the SelectArguments. Please refer to the Sorting Data with Data Source Controls topic in this regard.
2. Set the ASPxGridView.EnableRowsCache property to true. In this case, the ASPxGridView will fetch data from the underlying datasource only when it is necessary.
   Thanks,
   Plato

Hi Plato,
Thanks for your response. I have got following queries :

1. As you suggested, I have tried setting ASPxGridView.EnableRowsCache = true , but the gridview still keeps calling the Select method of its ObjectDataSource everytime there is a postback on the page, even via a button click outside the grid that has got nothing to do with the grid at all? I have also checked the documentation and and it says ASPxGridView.EnableRowsCache is true by default.
2. Is there a demo with code that explains how to implement IListServer interface to perform Paging, Sorting, Grouping, Filtering and Summary Calculation at database level using AspxGridview with ObjectDataSource with custom business objects?
   I have managed to implement Paging and Sorting at database level using ObjectDataSource parameters PageSize, StartRowIndex and Sort Expression but I would like to have Grouping, Filtering and Summary Calculation features as well.
   Awaiting
   Nabeel

Hi Nabeel,

1. I do not see this issue. Attached you will find a web site I used to test the DataSourceForceStandardPaging property. The PagingAndSorting\SortParameter.aspx page contains a button which sends a postback to the server. The debugger does not stop when I click this button if the breakpoint is set in the Select method.
2. We do not have such a demo, sorry. This is a rather complicated interface and the only demo you can use is our own source code where this interface is implemented. Some information about this interface can be found in the Does the XtraGrid support Virtual Load mode? article.
   Thanks,
   Plato

Hi Plato,
Thanks for sending the sample. I have found out why the Select method is being called every time there is a post back in my code.
The reason is I am binding the ASPxGridView to a collection of custom objects and I am handling ASPxGridView's HtmlRowCreated event in order to manipulate some web controls contained within the template columns. I am using ASPxGridView.GetRow(e.VisibleIndex) method to retrieve the underlying custom object as follows:-
 protected void ASPxGridView1_HtmlRowCreated(object sender, ASPxGridViewTableRowEventArgs e)
    {
        ASPxGridView gv = sender as ASPxGridView;
        //process only data rows
        if (e.RowType != GridViewRowType.Data) return;
        //get underline custom object
        CustomObject obj = gv.GetDataRow(e.VisibleIndex) as CustomObject ;
        if (obj == null) return;
        else
        {
            // do something
        }
    }
I have noticed that on a post back, HtmlRowCreated event is always called for each row, even on a button click outside the grid. And as soon as the GetRow() method is called for the first time in HtmlRowCreated , it goes into the Select method.
Now what I would like to know is, if this is the right behavior, then how do i get the underlying custom object? The underlying custom object is complex and have some child objects in it which I need to access in order to manipulate the web controls contained within the template columns.
I have attached the sample you sent modifying it a bit to replicate the behavior. Please have a look.
Regards,
Nabeel

Hi Nabeel,
This is the correct behavior. The grid is able to render using only values saved in its cache. However, if you need to obtain an object, the grid should bind to the DataSource. I do not see another way for the grid to obtain this object. Anyway, you can use your DataSource methods and locate the object by the e.KeyValue passed to the event handler.
Thanks,
Plato

Hi Plato,
I am a bit confuse with your response. First you are saying that the grid caches the data in order to render but then you are saying that if it needs the custom object it has to bind. Well if its caching the objects when the page loads first time then why does it need to rebind on the postack? Shouldn't it get the data from the cache? what would be the point of caching then?
When the page loads first time, the Select method is called and in the HtmlRowCreated event for each row, e.GetRow() method works normally without calling the select method again. However when the postback happens e.g. a button click, the HtmlRowCreated event is called again for each row, but this time, the first call to e.GetRow() results in calling the Select method. Why is it making the call to Select method if it is already caching the data ?
Regards,
Nabeel

In the standard asp.net grid, the underlying object can be retrieve by casting e.DataItem in the RowDataBound event, but RowDatabound event is raised only if the grid is bind. In ASPxGridView , HtmlRowCreated event is raised not just when the grid is bind, infact it is raised everytime there is a postback. The code in the eventhandler requires the underlying data object to render template cells properly. I do e.GetRow() to get the data object. It works fine when the page is load first time but on a postback it results in calling Select method, which is a total waste of time and memory. I should be able to get it from the cache rite? How should i do that?
Awaiting
Nabeel