How to sort a DataGridView with Iset as datasource ?

kerseub · **Posted:** Thu Jul 26, 2007 4:14 am

Hibernate version: 1.2.0.4000
Mapping documents: really usefull here ?
Name and version of the database you are using: SQL Server 2005

Hi everyone, I'm using the CreateCriteria Method to create an IList.
Then I cast this IList to an ArrayList which is finally specified as datasource to a DataGridView. Clearly :

Code:

ArrayList liste = (ArrayList)this._session.CreateCriteria(typeof(MyWonderObject)).List();
dataGridView1.datasource=liste

Then the list is displayed correctly (that is not so bad) but it is impossible to sort it on another Column with a clic on a ColumnHeader.

Could you explain me why? How could I give an Iset as a datadource AND keep the datagrid's sort functionalities?
P.S.: MyWonderObject is already Implementing Equals() and compareTo() methods.
Thanks in advance.

Kerseub

gpolevoy · **Joined:** Tue Jul 24, 2007 3:27 pm **Posts:** 3

The problem is, when you are initializing DataSource property with a IEnumerable, ASPNET can't guess, how expensive is the iteration.

It could actually be lazily fetching the rows from database while iterating, and it can be the case with NHibernate lazy loading.

ASPNET can't make the hard decision to load and cache your IEnumerable in internal collection just to enable sorting.

When you are using a disconnected object instantiated in memory, such as an ArrayList or a DataSourceView everyting is ok, but you lose your lazy behavior.

You can wrap your select method in ObjectDataSource control, and have NHibernate load only a small part of the list for one page on sorting request:

http://msdn2.microsoft.com/en-us/library/sa88ktts.aspx

DavyBrion · **Posted:** Thu Jul 26, 2007 12:27 pm

kerseub wrote:

Hibernate version: 1.2.0.4000
Mapping documents: really usefull here ?
Name and version of the database you are using: SQL Server 2005

Hi everyone, I'm using the CreateCriteria Method to create an IList.
Then I cast this IList to an ArrayList which is finally specified as datasource to a DataGridView. Clearly :

Code:

ArrayList liste = (ArrayList)this._session.CreateCriteria(typeof(MyWonderObject)).List();
dataGridView1.datasource=liste

Then the list is displayed correctly (that is not so bad) but it is impossible to sort it on another Column with a clic on a ColumnHeader.

Could you explain me why? How could I give an Iset as a datadource AND keep the datagrid's sort functionalities?
P.S.: MyWonderObject is already Implementing Equals() and compareTo() methods.
Thanks in advance.

Kerseub

The datagridview only supports sorting datatables or dataviews if i recall correctly. Create a List based on your ISet (just pass it to the constructor... it implements IEnumerable so the List constructor will accept it) and then you can use Mark Brooks' DynamicComparer to easily (and very efficiently) sort the list based on the sortexpression of the DataGridView.

You can find an example of how to use the DynamicComparer here:
http://ralinx.wordpress.com/2007/07/02/ ... f-objects/

it provides very fast sorting and you don't have to do anything for it... it's very nice. All you need to do is implement the sort method of the DataGridView (or is it the sort method of the ObjectDataSource... i'm not sure on that one)... you can simply pass the sortexpression from the DataGridView to the DynamicComparer and the list will be sorted nicely.