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DevExpress ASP.NET Controls

Printed From: IdeaBlade
Category: DevForce
Forum Name: DevForce Classic
Forum Discription: For .NET 2.0
URL: http://www.ideablade.com/forum/forum_posts.asp?TID=386
Printed Date: 11-Jun-2026 at 10:37pm


Topic: DevExpress ASP.NET Controls
Posted By: -ook
Subject: DevExpress ASP.NET Controls
Date Posted: 27-Aug-2007 at 3:47pm
I have gone through the ASP Advanced tutorial and have managed to bind DevForce database objects to standard ASP.NET controls such the the GridView. However, when I use the DevExpress grid control (ASPxGridControl or ASPxPivotGrid) I receive the following error when specifying the DevForceDataSource as the grids datasource:

"An unhandled exception has occured.
Dataset does not support System.Nullable<>"

So, what can I do to resolve this problem?

Also, is there any documentation regarding using DevForce objects in ASP.NET applications other than the tutorial?

Thanks


Replies:
Posted By: davidklitzke
Date Posted: 27-Aug-2007 at 7:54pm
The DevExpress Web controls are dataset based, not object based, and do not support nullable objects. (it's not our fault that they don't support objects!).  My recommendation (if you want to use DevExpress controls on the Web) is to use a few .NET Web controls such as the GridView and the DetailsView (that support object datasources) and adorn them with DevExpress Web controls.  For example, you can start with the .NET DetailsView, bind then to IdeaBlade business objects, and add DevExpress components and get a very nice looking composite control.

Posted By: davidklitzke
Date Posted: 27-Aug-2007 at 8:07pm
Improved ASP.NET documentation, ease of use, and functionality is planned for the September 17, release.

Posted By: -ook
Date Posted: 27-Aug-2007 at 8:08pm
Which is no use if I want to use the DevExpress ASPxPivotGrid.

So in short the answer is that DevForce cannot be used in any meaningful way for [DevExpress] web applications.  Pity.

Posted By: -ook
Date Posted: 27-Aug-2007 at 8:10pm
Perhaps I spoke too soon. Will the Sept 17 release support the ASPxPivotGrid from DevExpress?

Posted By: davidklitzke
Date Posted: 27-Aug-2007 at 9:37pm
I did some more testing with the DevExpress web controls.  In particular, I looked at the ASPxGridControl.  Like you, I see the message on the Grid Control:  "An unhandled exception has occured.   Dataset does not support System.Nullable<>".  However, the interesting thing is that the control seems to be completely functional.  I can add and delete columns, change column widths, etc.  When I run my application,  the grid displays pretty much the same way it does when I display the .NET GridView.  Please try this and see if you can detect any loss of functionality.

Posted By: -ook
Date Posted: 28-Aug-2007 at 3:12pm
You are indeed correct, it works for the ASPxGridView. I shall test it now for the ASPxPivotGrid. Thanks

Posted By: -ook
Date Posted: 28-Aug-2007 at 3:37pm
It works with the ASPxPivotGrid too! I was too negatively judgmental in my earlier post. It is still irritating to not have design time access to the DevExpress control though. Is there anything I can add to the DevForceDataSource to fool the DevExpress design time control into believing a fully supported Datasource is supplied. In other words how can I stop the 'DataSet does not support System.Nullable<>' error?

Thanks

Posted By: davidklitzke
Date Posted: 28-Aug-2007 at 3:47pm
I'll need to have a discussion with DeveloperExpress on this matter.  I think that you have an excellent suggestion, and I agree with you that this would be a great enhancement to our story about supporting ASP.NET with DevForce.

Posted By: davidklitzke
Date Posted: 31-Aug-2007 at 8:13pm
I fixed the problem with the Designer when using DevExpress Web controls.  This capability will be available in our next release.
 
The problem occured when trying to add Nullable columns (which are not permitted in DevExpress Web components).  Instead of throwing an error and displaying an ugly error message, I now catch the error and skip over the column (which can't be used anyway).  If you are going to use DevEx for ASP.NET, you had better get rid of your hullable columns.  This is a DevEx limitation, not a DevForce limitation.
 

Posted By: -ook
Date Posted: 02-Sep-2007 at 2:01am
Thankyou David.

Now just to be clear, DevExpress does not support defined database fields that allow null values?

And the fix for the next release, is that the DevForce object datasource will automatically ignore the error? or the developer manually removing the 'nullable' fields?

And the next version of DevForce will be when? And what version of DevExpress will it support?

Thanks

Posted By: davidklitzke
Date Posted: 05-Sep-2007 at 8:47am
I'm still looking into the DevExpress support.  I do know that everything now works correctly even if I try to use nullable columns , and there are no designer errors.  However, none of the nullable columns shows up in the designer.  I fixed the Designer problem by throwing away the nullable columns in the designtime data.  What I don't know is what will happen if I tell the DevExpress GridView that the nullable columns are NOT nullable.  My intuition is that I can get the columns to show up in the designtime data (and maybe even in the list of available columns).  If this works, I also have to test the case of what the GridView will do if I try to display data that contains nulls.  I should know more about DevExpress by the end of the week.
 
I suspect that this will all work with any recent version of DevExpress.
 
The new and much improved DevForce object datasource will be released on September 19

Posted By: davidklitzke
Date Posted: 11-Sep-2007 at 9:19am
I finally got nullable columns to work with the ASPxGridView and ASPxPivotGrid, so at this point, there are no known limitations or bugs with respect to using DevExpress web controls.


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