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ASP.NET developers often encounter the problem of transferring server side
control values from one page to another using Server.Transfer ("PageName", true) method. Usual syntax of Request.Form doesn't work if you try to access the value of server side control from the redirected page. Developers often encounter this error:
"View state is invalid and might be corrupted error message when you use
Server.Transfer ("page name", true)"
Cause
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.
To resolve this problem, use one of the following methods.
Resolution 1: If you have many controls, and if you want to access the properties of these controls from another page, you can also declare those controls as public variables. For example:
Page1.aspx
Public Class Page1
Public WithEvents TextBox1 as System.Web.UI.WebControls.TextBox
'Insert your code here.
End Class
Page2.aspx
Dim sourcePage As Page1
SourcePage = CType (Context.Handler, System.Web.UI.Page)
Response.Write(sourcePage.TextBox1.Text)
Do not pass the second parameter (which is false by default) when you call
Server.Transfer. For example:
Server.Transfer ("<page name>")
This code does not send the QueryString and the Form fields to the page that
is called. When no data is transferred, ASP.NET does not run the message
authentication check.
Resolution 2: This option doesn't require controls to be defined as public variables.
Page1.aspx
Public Class Page1
Protected WithEvents TextBox1 as System.Web.UI.WebControls.TextBox
'Insert your code here.
End Class
Page2.aspx
Dim sourcePage As Page1
Dim sourceControl as TextBox
sourcePage = CType(Context.Handler, System.Web.UI.Page)
SourceControl = CType
(sourcePage.FindControl("TextBox1"),
System.Web.UI.Control)
Response.Write (SourceControl.Text)
