Hello Imar,

in chapter 4, you explain the ASP.NET state engine.

Why there are two overlapping properties to set the view state of server controls - I mean ViewStateMode and EnableViewState - and not just one ?

Why the TextBox control has both properties despite it does not use view state to maintain its value ?


Thank you

Antonius

Hi Antonius,

1) This is for legacy reasons. EnableViewState has been in the framework forever. When ViewStateMode was implemented, the designers of ASP.NET couldn't modify the behavior of EnableViewState as that would have broken millions of sites. That's why they introduced the new property to give you more control.

2) The properties are implemented on the base Control so all controls inherit them. TextBox *can* use View State; it just doesn't need it to keep track of the value the user supplies when posting back. If you set up, say, a TextChanged event handler, ViewState is used to store the old value so ASP.NET can compare the old and new value on the server and raise the event when the data is different.

Hope this helps,

Imar

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Imar Spaanjaars
http://Imar.Spaanjaars.Com
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Author of Beginning ASP.NET 4.5 : in C# and VB, Beginning ASP.NET Web Pages with WebMatrix
and Beginning ASP.NET 4 : in C# and VB.
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