asp.net 3.5 ajax maskededitextender error
i am new in asp.net with Ajax. I'm trying to use maskededitextender but displaying following error
pls pls help me someone. will be very much grateful
Server Error in '/TEST' Application.
Could
not load type 'System.Web.UI.ScriptReferenceBase' from assembly
'System.Web.Extensions, Version=3.5.0.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35'.
Description: An
unhandled exception occurred during the execution of the current web
request. Please review the stack trace for more information about the
error and where it originated in the code.
Exception Details: System.TypeLoadException:
Could not load type 'System.Web.UI.ScriptReferenceBase' from assembly
'System.Web.Extensions, Version=3.5.0.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35'.