asp.net - Help: Error = NullReferenceException was unhandled by user code -

any appreciated... code works cleanly until error...

error occuring @ line: sqldatasource3.updateparameters("techid").defaultvalue() = cint(technicianrow("techid"))

here full vb code:

imports system.data  partial class incidentassignment     inherits system.web.ui.page      public incidentrow datarowview     public technicianrow datarowview      protected sub button1_click(byval sender object, byval e system.eventargs) handles button1.click          'check see if incident has been selected          if gridview1.selectedindex = -1             button1.commandname = ""             lblmessage.text = "you must select incident."          else             button1.commandname = "nextview"             lblmessage.text = ""           end if     end sub      protected sub button3_click(byval sender object, byval e system.eventargs) handles button3.click          'check see if incident has been selected          if gridview2.selectedindex = -1             button3.commandname = ""             lblmessage2.text = "you must select technician."          else             button3.commandname = "nextview"             lblmessage2.text = ""             'create second dataview              dim technicianstable dataview = ctype(sqldatasource2.select(datasourceselectarguments.empty), dataview)               'save selected technician data row              'to datarowview object , session state              technicianrow = technicianstable(gridview2.selectedindex)              session("technician") = technicianrow              'create dataview              dim incidentstable dataview = ctype(sqldatasource1.select(datasourceselectarguments.empty), dataview)              'save pageindex , pagesize variables.              dim pageindex integer = gridview1.pageindex              dim pagesize integer = gridview1.pagesize                'calculate value of selectedindex              dim selectedindex integer = (pageindex * pagesize) + gridview1.selectedindex              'save selected data row datarowview              'object , session state              incidentrow = incidentstable(selectedindex)              session("incident") = incidentrow              'display output 2 datarowview objects              label1.text = incidentrow("name")              label2.text = incidentrow("productcode")              label3.text = technicianrow("name")          end if      end sub        public sub btnassign_click(byval sender object, byval e system.eventargs) handles btnassign.click          'assign data session state          'the 2 datarowview objects  ***error technicianrow = ctype(session("technician"), datarowview)          incidentrow = ctype(session("incident"), datarowview)           'update value of 2 parameters          'used store new information          'assigned technician            sqldatasource3.updateparameters("techid").defaultvalue() = cint(technicianrow("techid"))          sqldatasource3.updateparameters("incidentid").defaultvalue() = cint(incidentrow("incidentid"))           'trap errors          try              'update table.              sqldatasource3.update()                'unselect 2 gridview controls              gridview1.selectedindex = -1              gridview2.selectedindex = -1               'rebind gridview controls              gridview1.databind()              gridview2.databind()               'move first view              multiview1.activeviewindex = 0          catch ex exception              session("exception") = ex              session("page") = "~/admin/indicentassignment.aspx"              response.redirect("~/errormessage.aspx")          end try      end sub      protected sub gridview2_selectedindexchanged(byval sender object, byval e system.eventargs) handles gridview2.selectedindexchanged      end sub end class 

remove parenthesis ".defaultvalue()

do have parameters defined on sqldatasource in page??

 updateparameters>               <asp:parameter name="somename" type="string" />               <asp:parameter name="somedescription" type="string" />             </updateparameters>