BindingSource - A Closer Look...

re: BindingSource - A Closer Look...

mihailik — Wed, 16 Mar 2005 11:17:00 GMT

Excellent! I like this classes very much, I cannot wait Whidbey to be released :-)

re: BindingSource - A Closer Look...

Dinesh Chandnani — Wed, 16 Mar 2005 18:01:00 GMT

Yes - these classes are really cool!

One thing I should mention - though I mention DataTable in the section 'Binding to IList and IListSource', in reality, binding to a DataTable really behaves like Binding to IBindingListView. This is because a DataTable is an IListSource and it's getList method returns a DataView which is a IBindingListViewView. DataView is aware of all the changes to the DataTable i.e. row added/deleted/value changed/etc. So if you bind to a DataTable through a DataView you will see all the changes made to the DataTable since ListChanged events will be fired.

Thanks,
-Dinesh

re: BindingSource - A Closer Look...

Michael Weinhardt — Fri, 25 Mar 2005 00:21:00 GMT

Hi Dinesh,

I'm wondering if this entry describes the features that will be available from the BindingSource, or that are available from the BindingSource.

For example, I'm using the Feb CTP and, if I bind to IEnumerable from a DGV, via a BindingSource, I get a read-only DGV.

Also, if I build a custom BindingList<T> that implements sorting, say, then set it as the BindingSource's data source using the designer eg

public class MyDataSource : CustomBindingList<Person> {}
public class SortableBindingList<T> : BindingList<T> {
//IBindingList sorting imp.
}

this.bobBindingSource.DataSource = typeof(WindowsApplication1.bob)

When it comes to running the app, the sorting disappears, suggesting a new BindingList is created in place of the one I thought I'd specified.

Is the end goal to basically take any type and turn it into a BindingList (unless alreaedy one) as you suggest?

Cheers,
Michael Weinhardt

re: BindingSource - A Closer Look...

Dinesh Chandnani — Fri, 25 Mar 2005 05:38:00 GMT

Hello Michael,

These features are currently available in BindingSource.

When you bind IEnumerable to a BindingSource whioch is bound to a DGV, BindingSource basically checks to see if the object in the list has a default public constructor. If it does, then it will allow new objects to be added in the list and the DGV will thus be read/write. However, if the object does not have a public default constructor then the BindingSource cannot add new objects to the list and so the DGV will end up being read-only. So, you will have to add a public default constructor to the object to have a read-write DGV.

When you bind to a BindingSource by specifying a type, yes, the BindingSource creates a BindingList<T> internally of the type specified. So in the case above, BindingSource created BindingList<typeof(WindowsApplication1.bob)>. If you want to allow sorting you can set the datasource of BindingSource to be the SortableBindingList<T>.

SortableBindingList<Customer> sbList = new SortableBindingList<Customer>();
this.bindingSource.DataSource = sbList; // Now sorting will work fine

So, if the DataSource is an IList, IListSource, IBindingList or IBindingListView, the BindingSource will not create an internal BindingList<T>.

So end goal is to turn it into a BindingList if it is anything "lesser" than an IList, or to keep it as IList or IListSource if it is one of these already.

Please let me know if you have any more questions.

Thanks,
-Dinesh Chandnani

re: BindingSource - A Closer Look...

Michael Weinhardt — Mon, 28 Mar 2005 08:42:00 GMT

Hi Dinesh, I don't see the IEnumerable behavior you are describing ie it remains read-only when bound to a DGV via a BindingSource eg: public class Person { public string Name { ... } public int Age { ... } } public class Persons : IEnumerable { ... } public partial class Form1 : Form { public Form1() { InitializeComponent(); Persons persons = new Persons(); BindingSource bs = new BindingSource(persons, null); this.dataGridView1.DataSource = bs; } } Also, why is there are difference between me setting a BindingSource's data source using the designer (BindingSource.DataSource = typeof(mySortableType); vs run-time (BindingSource.DataSource = new mySortabletype();. What I mean by that is, if I can set the BindingSource with a DataSource that provides sorting, from the designer, I expect the sorting to be retained when run. I don't expect to have to write additional code to, essentially, reseed the BindingSource with the desired data source. BTW I actually love the BindingSource and the Data Binding improvements, but the design-time/run-time differences concern me. What am I missing? Thanks Dinesh! Michael

Details of .NET 2.0 Data Binding

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re: BindingSource - A Closer Look...

dchandnani — Sun, 14 Aug 2005 21:09:42 GMT

In case of IEnumerable, you will need to set AllowNew property of BindingSource to true. Please let me know of any questions.

Regards,
-Dinesh Chandnani

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http://updatecontrols.net

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