ASP.NET Add Control on postback

Question

Hi,

I've put together a simple form to highlight the concepts of dynamic forms. What I need to do is add a control to the page when the user clicks the "Add" button.

I have a simple counter at the moment that stores the amount of controls created, which is incremented when the button is clicked.

At first I thought it would be as simple as calling RecreateChildControls (the class inherits from CompositeControl) on the event handler. This does create the new controls based on the incremented value, but all the control state is lost. I'm assuming this is because the event has been fired after the Init & Load phase.

Is there any other way to do this? I can get it to work by inspecting the postback value on the Init event, however this seems to be a little hacky.

Answer 1

Use PlaceHolders, I have run into the same issue before :)

Answer 2

This does create the new controls based on the incremented value, but all the control state is lost.

You're calling the function too late in the page life cycle. State is applied to your controls for the "Load" stage, and so if the controls are not created before that stage the state won't be restored, because the controls don't exist when it tries to apply the state.

You need to create the controls in the Page's Init event.

Personally, I'm not a fan of dynamic controls in ASP.Net. They have their place, but more often I choose a suitable maximum number of allowed controls, put them all on the page initially, and only enable/disable/hide/show them as needed.