Can anybody shed any light onto this weird problem which I have experienced before (and had to code around) but finally found the reason for.

If you have a dropdownlist on a page which uses a MasterPage and the EnableViewState is set to false in the MasterPage and then enabled on a page-by-page basis, the DropDownList_SelectedIndexChanged event is fired for all DropDownLists regardless of which one is actually called. It isn't important that the view state is enabled on a page-by-page basis, the important thing seems to be that it is disabled in the masterpage.

This problem is also reported in the following post http://forums.asp.net/p/1163948/1931200.aspx but nobody seems to have an answer.

Any help is appreciated.

Thanks,

Chris

 Yes. Because the maserpage has EnableViewState with false, the page will not keep the view state. By default, the SelectedIndex of a DropdownList control will be 0, and SelectedIndex property of RadioButtonList will be -1. If the selected index is not queal to the default value, the SelectedIndexChanged event will always fired. To test it, you can selected the second item or third item ect but not the first one, the event is fired. It is right. and then, select the first item(index=0) of dropdownlist you will find the event will not be fired. Right. the default selectedindex the page remember is 0. Therefore, to solve such problem, the only approach is to set the EnableViewState property of Master and Page to true. If you need to set it to false, I am afraid you have to try to find some way to avoid to set the EnableViewState to false.

Thanks for the reply.

I understand what you are saying whereby the check is based on "If selectedIndex is not equal to the defaultvalue then fire the event". Is this always the case or does it only work this way when EnableViewState=false? For example, if EnableViewState=True and I select item 3 and then select item 0, will the event be fired?

Regardless of this however, if I am setting EnableViewState=Flase in the MasterPage, but then set EnableViewState=True in each individual page or on each individual control, why does this not work? Surely the setting on the content page should overwrite the settign of the MasterPage?

Any idea?

Thanks, Chris

Actually, master page plays a server control of content page at runtime. Scott Allen says:

For ViewState to be available to a control, it's parent must have ViewState enabled. Since a master page injects itself as the direct child of the Page object, having ViewState disabled in the master page shuts off ViewState for everything inside the Page.

For the entire article please see: http://odetocode.com/Blogs/scott/archive/2006/10/11/7872.aspx 

May this helps you! 

 hello again,

To solve you problem, I suggest that you don't set EnableViewState="false" in master directive, but set it in Web.config.

<system.web>

   <pages enableViewState="false"  />

</system.web>

If the page you mentioned above just set the EnableViewState="true" in Page directive.

more information still see: http://odetocode.com/Blogs/scott/archive/2006/10/11/7872.aspx