c# - How to use Delegate actions as a parameter? -

i used delegate action parameter in method follows:

private ienumerable<sc.serverpathservices.gafpfileinfo> startprojectarchive(int32 projectid, int32 sourceserverpathid, action uirefresh,action<ienumerable<projectfile>> popupfiles) 

here have 2 delegates. have problem popupfiles delegate.

i calling in method passing list of files parameter popupfiles follows:

 if(popupfiles!=null)                    popupfiles(filesmodifiedinsourceserver); 

here filesmodifiedinsourceserver contains list of files. calling in code behind file follows:

archiveresponse = projectmanager.startprojectarchive(projectid, 0, () =>                      {                          foreach (control control in tdfilelist.controls.cast<control>())                          {                              if (control dell.afp.usercontrol.projectfilelistbasecontrol)                              {                                  ((projectfilelistbasecontrol)control).refresh();                              }                          }                      },                      (filesmodifiedinsourceserver)=>                          {                              if (filesmodifiedinsourceserver != null && filesmodifiedinsourceserver.count > 0)                              {                              popupmodifiedfiles(filesmodifiedinsourceserver);                              }                          }); 

but in above code when passing parameter delegate action popupfiles used filesmodifiedinsourceserver parameter. giving me error delegate action not take 1 argument. how else can pass parameter? resolved. getting object reference error while calling method. not know why throwing object reference error.