SystemAccount的访问权限异常

Question

我在System Acoount中运行了一些SP-Code。但即使有这个用户，我仍然会收到拒绝接入的访问权限。我还尝试了其他用户帐户（具有管理员权限）

错误讯息：

Attempted to perform an unauthorized operation.   
 at Microsoft.SharePoint.SPGlobal.HandleUnauthorizedAccessException(UnauthorizedAccessException ex)    
 at Microsoft.SharePoint.SPSecurableObject.CheckPermissions(SPBasePermissions permissionMask)    
 at Microsoft.SharePoint.SPRoleAssignmentCollection.Init()    
 at Microsoft.SharePoint.SPBaseCollection.GetEnumerator()    
 at OLXPermissionEventReceiver.OLXPermissionEventReceiver.OLXPermissionEventReceiver.<>c__DisplayClass1.<SetPermissionsToListItem>b__0()

代码：

        SPSecurity.RunWithElevatedPrivileges(delegate()
        {
            try
            {


                SPSite tmpSite = new SPSite("Http://example.com);

                SPUserToken sysUser = tmpSite.SystemAccount.UserToken;

                using (SPSite site = new SPSite(siteUrl, sysUser))
                {
                    using (SPWeb web = site.OpenWeb())
                    {
                        try
                        {
                            SPPrincipal principal = (SPPrincipal) group;                                                             
                            item.BreakRoleInheritance(false);                             
                            web.AllowUnsafeUpdates = true; 
                            // Works until here
                            List<SPRoleAssignment> roleAssignmentList = new List<SPRoleAssignment>();
                            bool cateringRoleFound = false;
                            foreach (SPRoleAssignment roleAssignment in item.RoleAssignments)
                            {

                            }

                        }
                    }
                }
            }
        }

看起来像“foreach” - 循环正在抛出错误。有什么想法吗？