DataGridView and NHibernate, updating the database on edit

windcape · **Joined:** Wed Oct 17, 2007 12:14 am **Posts:** 1

Hey

I've been struggeling with this for a while. Is it even possible to use NHibernate and databind it to a DataGridView, and then provide object updates using the ISession ?

I read tons of posts, articles and stuff, but everything is towards READ ONLY. I wish to have EDITABLE data, and be able to add NEW rows, and actually SAVE them in the database afterwards.

I don't see .NET providing me able to do this, as EventListeners such as CellEndEdit only can provide column number, not return the actually object.
I've also looked into http://nhibernate.fluffnstuff.org/ , but it's so poorly documentated, and again only towards READING , or just visual read-only binding in Visual Studio.

Is it totaly impossible to make a DataGridView with editable data, that also will be updated in a database later ? Some users of nhibernate MUST have tried this before, and I would REALLY appreciate help/example on how to do this.

Thanks.

Tolomaüs · **Joined:** Sat Jul 21, 2007 3:56 pm **Posts:** 27

Hello windcape,

I have been struggling with the same problems as you describe. But in the end I created my own solution for it.

It is based on Csla's framework, but to get it 100% working (including inline adding and deleting) I had to make my own subclasses of it.

As far as documentation, I will have to disappoint you, because - apart from a lot of comments in the code - there is none available at the moment.

Anyway, if you want to try it, you can find it here: http://www.paarden.be/NHibernate/ObjectFramework.zip Look for the OrganisationsViewer or ClientViewer in the HorsesConfigurator project.

Feel free to ask questions or post your remarks.

Tolomaüs.

jlockwood · **Posted:** Thu Oct 18, 2007 11:49 pm

I've done this a few times before. It's a bit of a pain in the rear because I ended up handling the update and insert events manually.

For starters, to populate the GridView I used a DAO as a wrapper like so:

Code:

<asp:ObjectDataSource ID="UserHistoryDataSource" runat="server" SelectMethod="GetAll"
        TypeName="UserHistoryDao">
</asp:ObjectDataSource>

or you can use a dao factory:

Code:

<asp:ObjectDataSource ID="UserHistoryDataSource" runat="server"
                    SelectMethod="GetAll" TypeName="NHibernateDaoFactory+UserHistoryDao">
</asp:ObjectDataSource>

the type UserHistoryDao is used to get all user history records. UserHistoryDataSource is then used with the GridView to populate the grid. Each entity has a property ID that serves as the surrogate key. To retrieve selected items you have to add DataKeyNames="ID" so that the IDs for your entities are available.

To bind properties of classes on the main class bound, you use something like this (on templated column):

Code:

Text='<%# Eval("Name.First") %>'

in the ItemTemplate, This would display the value in UserHistory.Name.First.

I don't have a working example of update and insert on hand, but here's the part that get's most people. You need to make sure that you cancel the update before returning control:

Code:

    Protected Sub WaterMeterModelsView_RowUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles WaterMeterModelsView.RowUpdating
        ...
        'Update Code
        'If I remember right, you get the ID from  e.Keys("ID")
        ...

        e.Cancel = True
    End Sub

Inserts are similar, but I hate the inline inserts (I ended up with complex insert templates because of my object graph). I tend to use the insert button on the grid, but when clicked I cancel the insert and redirect the user to an insert page (just my preference).

Quote:

I don't see .NET providing me able to do this, as EventListeners such as CellEndEdit only can provide column number, not return the actually object.

You're right, I'm not aware of a way to get a whole object, but even if you could it would no longer be associated with the session/cache and would force you to make all your entities serializable.

It's a little awkward, but you can make the datagrid (appear) to work like you want id to. If you wanted the DataGrid to do all the work, I think you'd have to have DAOs that work in terms of DataSets (I forget the exact interface supported).