Silverlight datagrid virtualization with custom control

Question

I have a data grid in my silverlight 4 application. I have also made a custom textbox that only takes numeric values and does a couple of other specific things. I also added a decimal dependency property on my custom control that I bind to, that pretty much returns a formatted version of Text that the control inherits from TextBox.

I then bind the datagrid's itemssource to an observablecolletion. I also added my custom control as one of the columns in the datagrid using DataGridTemplateColumn.

Everything works fine except the datagrid's virtualization. If I add an item to the dataGrid, edit the value in my custom Control, delete the row and then add a brand new row (a complete new instance) the value in my custom control is the value of the deleted row. And to clear up, it is not a binding mistake or anything like that. The problem is that the constructor of my custom textbox is not being called and also the binding is not updated until i change the actual value in my custom control. The datagrid's virtualization is re-using previously created controls.

I do not want to turn off virtualization. Is there a way to specify how my custom control should be recycled (virtualized)? Or perhaps an event that is fire when Controls are virtualized or recycled?

Any help will be much appreciated.

Answer 1

Is there any chance you can upgrade to Silverlight 5? In SL 5 you have the DataContextChanged event which I think should be a good way of detecting when the control is reused to draw another row.

If SL 5 is not an option you may be able to catch it in the Loaded event. I am not entirely sure, but I think Loaded should be fired when the control is reused. Then whenever Loaded is fired, save the current DataContext to a temp variable. When Loaded is fired next time you can compare the old DataContext to the current one and if it has changed, re-run your logic as needed.