c# - Can I merge these two lists in 1 go -

what trying do,

// members sharepoint list (can null) // members database (can null) // merge database members sharepoint list members database members should have property vip = true // merge mean if not in list add them list, if in list change there property vip = true // default vip property false 

what have developed far,

list<member> members = new list<member>();         foreach (splistitem mitem in getlist(url).items)         {             member m = new member();             m.id = mitem.id;             m.name = mitem.title;             m.company = utilities.objecttostringorempty(mitem[companycol]);             m.email = utilities.objecttostringorempty(mitem[emailcol]);             m.comment = utilities.objecttostringorempty(mitem[commentcol]);             m.membership = utilities.objecttostringorempty(mitem[mscol]);             members.add(m);         }          var cd = new membermanager().getmoremembers(url + "/");         var activemembers = cd.where(am => am.membershipstatus == "active" || am.membershipstatus == "pending").tolist();         if (activemembers != null || activemembers.count() > 0)         {             foreach (var in activemembers)             {                 if (!members.any(a => a.email.tolowerinvariant() == am.email.tolowerinvariant()))                 {                     member m = new member();                     m.name = am.firstname + " " + am.lastname;                     m.email = am.email;                     m.isvip = true;                     members.add(m);                 }             }         }          md.members = members.toarray(); 

problem

can use linq , merge these lists in single go ? maybe this, pseudo be

var dbmembers = //getdbmembers active or pending  var spmembers =                select members using `.cast<splistitem>()`               if spmembers has dbmember (compared email)               change spmembers vip property true (which default false)               rest dbmembers doesn't exists in spmembers, add them vip property = true 

not sure how can efficiently put above pseudo code linq

try this:

var allspmembers = getsplist(); // members mentioned before `.cast<splistitem>()`  list<splistitem> spmembers =     dbmembers.groupjoin(allspmembers, dbm => dbm.email, spm => spm.email,         (dbmember, spmember) => new { dbmember, spmember })              .selectmany(x => x.spmember.defaultifempty(), (x, spmember) =>                  {                      splistitem yoursplistitem;                       if (spmember != null)                      {                          yoursplistitem = spmember;                      }                      else                      {                          yoursplistitem = x.dbmember; //make mapping here splistitem model                      }                       yoursplistitem.vip = true;                       return yoursplistitem;                  }).tolist();