ViewState is Corrupt or Invalid for this page
When you access the Server.transfer("Pagename","true") utility in an aspx page,
you will get the following error.
State is invalid for this page and might be corrupted
This problem occurs because the EnableViewStateMac attribute of the
<pages> element is set to true by default. When this attribute is set to
true, ASP.NET runs a message authentication check (MAC) on the view state of
the page when the page is posted back from the client. This check determines if
the view state of the page was modified on the client. For security purposes,
it is recommended that you keep this attribute set to true.
When you call the Server.Transfer method and set the second parameter to true,
you preserve the QueryString and the Form collections. One of the form fields
is the hidden __VIEWSTATE form field, which holds the view state for the page.
The view state message authentication check fails because the message
authentication check only checks each page. Therefore, the view state from the
page that calls Server.Transfer is not valid on the destination page.
View state is page scoped and is valid for that page only. View state should
not be transferred across pages
For more detail on this error and resolution, refer the following links
PRB: "View State Is Invalid" Error Message When You Use Server.Transfer
If you didnt get this error because of this reason, then refer this links to
know more details about viewstate problems.
FIX: "The View State Is Invalid for This Page and Might Be Corrupted" Error
Message in ASP.NET
View State is corrupted when view state contains object that have long decimals