Update records using LINQ

Question

I need to set a value in a table for a subset of rows  In SQL  I would do this   UPDATE dbo Person SET is default   0 WHERE person id   5   Is there a way to do this in LINQ   I currently use the   var result    from p in Context People        notation   Is there an update method I can use  Or do I have to get all the records  then update them one-by-one in a Foreach   Is this the most efficient way  if this is even possible    from p in Context person account portfolio where p person id    personId select p      ToList       ForEach         x   gt         x is default          false

User · Answer

You have two options as far as I know    Perform your query  iterate over it to modify the entities  then call SaveChanges    Execute a SQL command like you mentioned at the top of your question  To see how to do this  take a look at this page    If you use option 2  you re losing some of the abstraction that the Entity Framework gives you  but if you need to perform a very large update  this might be the best choice for performance reasons

User · Answer

I assume person id is the primary key of Person table  so here s how you update a single record   Person result    from p in Context Persons               where p person id    5               select p  SingleOrDefault     result is default   false   Context SaveChanges      and here s how you update multiple records   List lt Person gt  results    from p in Context Persons                         where         add where condition here                         select p  ToList     foreach  Person p in results        p is default   false     Context SaveChanges

User · Answer

Strangely  for me it s SubmitChanges as opposed to SaveChanges       foreach  var item in w                if  Convert ToInt32 e CommandArgument     item ID                        item Sort   1                    else                       item Sort   null                    db SubmitChanges

User · Answer

public ActionResult OrderDel int id                string a   Session  UserSession   ToString            var s    from test in ob Order Details where test Email ID Fk    a  amp  amp  test Order ID    id select test  FirstOrDefault            s Status    Order Cancel By User           ob SaveChanges              foreach var updter in s                            updter Status    Order Cancel By User                         return Json  Sucess   JsonRequestBehavior AllowGet          lt script gt              function Cancel id                    if  confirm  Are your sure   Want to Cancel                             ajax                            type   POST                           url    Url Action  OrderDel    Home       id                          datatype   JSON                           success  function  Result                                if  Result     Sucess                                                                 alert  Your Order has been Canceled                                      window location reload                                                                                     error  function  Msgerror                                alert Msgerror responseText                                                                                                lt  script gt

User · Answer

Yes  you have to get all records  update them and then call SaveChanges

User · Answer

Just as an addition to the accepted answer  you might find your code looking more consistent when using the LINQ method syntax   Context person account portfolio  Where p   gt  person id    personId   ToList    ForEach x   gt  x is default   false      ToList   is neccessary because  ForEach   is defined only on List lt T gt   not on IEnumerable lt T gt   Just be aware  ToList   is going to execute the query and load ALL matching rows from database before executing the loop

User · Answer

This worked best    from p in Context person account portfolio   where p person id    personId select p  ToList                                            ForEach x   gt  x is default   false    Context SaveChanges

User · Answer

Yes  You can use foreach to update the records in linq There is no performance degrade   you can verify that the standard Where operator is implemented using the yield construct introduced in C  2 0       The use of yield has an interesting benefit which is that the query is   not actually evaluated until it is iterated over  either with a   foreach statement or by manually using the underlying GetEnumerator   and MoveNext methods   For instance    var query   db Customers Where  c   gt  c Name StartsWith   A     query   query Where  c   gt  c Purchases Count    gt   2   var result   query Select  c   gt  c Name    foreach  string name in result       Only now is the query executed     Console WriteLine  name     Exceptional operators are  First  ElementAt  Sum  Average  All  Any  ToArray and ToList force immediate query evaluation   So no need to scare to use foreach for update the linq result   In your case code sample given below will be useful to update many properties      var persons    from p in Context person account portfolio where p person name    personName select p      TO update using foreach  foreach var person in persons      update property values       I hope it helps

[c#] Update records using LINQ

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