c# - issue attaching/adding an entity object which is detached from the DB Context? -

i new ef , seem have become bit stuck following issue..

i have following situation.

two applications using same database, , have both loaded context @ same time displaying same information.
application 1 goes , deletes entity , updates database savechanges. application 2 goes , saves same modified entity.

we using updategraph recurse through tree , save entities database context. however, when come saving deleted entity, doesn't exist in db context obtained database want add database.

i have tried doing add, gives multiplicity error trying add full tree context!

any ideas please?

the following code snippet updategraph extension method. (http://github.com/refactorthis/graphdiff)

private static void recursivegraphupdate<t>(dbcontext context, t datastoreentity, t updatingentity, updatemember member) t:class     {         if (member.iscollection)         {             // dealing collection             var updatevalues = (ienumerable)member.accessor.getvalue(updatingentity, null);             var dbcollection = (ienumerable)member.accessor.getvalue(datastoreentity, null);             var keyfields = context.getkeysfor(updatevalues.gettype().getgenericarguments()[0]);             var dbhash = mapcollectiontodictionary(keyfields, dbcollection);              // iterate through elements updated graph , try match them against db graph.             list<object> additions = new list<object>();             foreach (object updateitem in updatevalues)             {                 var key = createhash(keyfields, updateitem);                  // try find in db collection                 object dbitem;                 var itemid = updateitem.gettype().getproperty("id");                  if (dbhash.trygetvalue(key, out dbitem))                 {                      var property = updateitem.gettype().getproperty("deleted");                     bool ysn = property.getvalue(updateitem, null).tostring() == "true" ? true : false;                     if (ysn)                     {                         context.entry(dbitem).currentvalues.setvalues(updateitem);                         continue;                     }                      // if own collection                     if (member.isowned)                     {                         context.entry(dbitem).currentvalues.setvalues(updateitem); // match means updating                          foreach (var childmember in member.members)                             recursivegraphupdate(context, dbhash[key], updateitem, childmember);                     }                      dbhash.remove(key); // remove leave db removals in collection                 }                  else                     additions.add(updateitem);             }              // removal of dbitem's left in collection             foreach (var dbitem in dbhash.values)             {                 var property = dbitem.gettype().getproperty("deleted");                 bool ysn = property.getvalue(dbitem, null).tostring() == "true" ? true : false;                 if (ysn)                 {                     // own collection remove completely.                     if (member.isowned)                         context.set(dbitem.gettype()).remove(dbitem);                      dbcollection.gettype().getmethod("remove").invoke(dbcollection, new[] { dbitem });                 }             }              // add elements marked addition             foreach (object newitem in additions)             {                 if (!member.isowned)                     context.set(newitem.gettype()).attach(newitem);                  // otherwise add object                 dbcollection.gettype().getmethod("add").invoke(dbcollection, new[] { newitem });             }         }         else // not collection         {             var dbvalue = member.accessor.getvalue(datastoreentity, null);             var newvalue = member.accessor.getvalue(updatingentity, null);             if (dbvalue == null && newvalue == null) // no value                 return;              // if own collection need update entities otherwise simple relationship update             if (!member.isowned)             {                 if (dbvalue != null && newvalue != null)                 {                     var keyfields = context.getkeysfor(newvalue.gettype());                     var newkey = createhash(keyfields, newvalue);                     var updatekey = createhash(keyfields, dbvalue);                     if (newkey == updatekey)                         return; // nothing if same key                 }                  if (context.entry(newvalue).state == entitystate.detached)                     context.set(newvalue.gettype()).attach(newvalue);                  member.accessor.setvalue(datastoreentity, newvalue, null);                 context.entry(newvalue).reload();                 // todo this: context.entry(newvalue).state = entitystate.unchanged;                 // seems though in unchanged state ef still update database if original values different.             }             else             {                 if (dbvalue != null && newvalue != null)                 {                     // check if same key, if update values on entity                     var keyfields = context.getkeysfor(newvalue.gettype());                     var newkey = createhash(keyfields, newvalue);                     var updatekey = createhash(keyfields, dbvalue);                      // perform update if same                     if (updatekey == newkey)                     {                         context.entry(dbvalue).currentvalues.setvalues(newvalue);                         context.entry(dbvalue).state = entitystate.modified;                     }                     else                         member.accessor.setvalue(datastoreentity, newvalue, null);                 }                 else                     member.accessor.setvalue(datastoreentity, newvalue, null);                  // todo                 foreach (var childmember in member.members)                     recursivegraphupdate(context, dbvalue, newvalue, childmember);             }         }     }