ASP.NET 2.0 - Control State

Control State

I mentioned earlier that one of the most frustrating aspects of working with server-side controls in ASP.NET 1.x is the all-or-nothing mentality with respect to view state. Behavioral aspects of controls like pagination in the DataGrid or selection change notifications in textboxes require view state to be enabled to function properly. I'm sure all of you are sufficiently daunted by the prospect of leaving view state enabled in any of your DataGrids at this point. In ASP.NET 2.0, Microsoft addresses this particular problem by partitioning the view state into two separate and distinct categories: view state and control state.

Control state is another type of hidden state reserved exclusively for controls to maintain their core behavioral functionality, whereas view state only contains state to maintain the control's contents (UI). Technically, control state is stored in the same hidden field as view state (being just another leaf node at the end of the view state hierarchy), but if you disable view state on a particular control, or on an entire page, the control state is still propagated. The nice aspect of this implementation is that we can now amend our original principle on optimizing view state for ASP.NET 2.0 to be much stronger: if you populate the contents of a control every time a page is requested, you should disable view state for that control.

As long as control builders properly partition their state into behavioral state (to maintain core functionality) and UI state (to retain contents), this statement should be followed religiously. I would like to tell you to start following this recommendation now with all work done in ASP.NET 2.0, but the DataGrid has not been refactored to keep its behavioral state in control state. Fortunately, the new GridView is the logical successor to the DataGrid and it uses control state properly, as do the new versions of the TextBox and DropDownList controls.

Declarative Data Sources and View State

There is a small problem with the application of our view state optimization principle—you will very often not know whether you are populating the contents of a control on each request or not. The introduction of declarative data sources in ASP.NET 2.0 means that binding data to a control no longer involves explicitly wiring up its Data source property to a DataReader or DataSet and calling DataBind. Instead, you can declaratively place a data source on your page and point your control to that data source, for example using the new GridView class and an associated SqlDataSource bound to the authors table in the pubs database (see Figure 8). If you run this page, you will find that it just works. The GridView and its corresponding data source are smart enough to know when to interact. By the time the page is ready to render, the GridView is full of data from the data source and will properly render the entire authors table to the client.

http://msdn2.microsoft.com/en-us/magazine/cc163901.aspx