LINQ to Entities how to update a record

Question

Okay  so I m new to both EF and LINQ  I have figured out how to INSERT and DELETE but for some reason UPDATE seems to escape my grasp   Here is a sample of my code   EntityDB dataBase   new EntityDB    Customer c   new Customer        Name    Test        Gender    Male    dataBase Customers AddObject c   dataBase SaveChanges      The above creates and adds a record just fine   Customer c    from x in dataBase Customers              where x Name     Test               selext x  First    dataBase Customers DeleteObject c   dataBase SaveChanges      The above effectively deletes the specified record   Now how do I update  I can t seem to find an  UpdateObject    method on the entity collection

User · Answer

They both track your changes to the collection  just call the SaveChanges   method that should update the DB

User · Answer

for update   from x in dataBase Customers          where x Name     Test           select x  ToList   ForEach xx   gt  xx Name  New Name        for delete  dataBase Customers RemoveAll x  gt x Name   Name

User · Answer

In most cases  tster s answer will suffice  However  I had a scenario where I wanted to update a row without first retrieving it   My situation is this  I ve got a table where I want to  lock  a row so that only a single user at a time will be able to edit it in my app  I m achieving this by saying   update items set status    in use   lastuser    lastuser  lastupdate    updatetime where ID    rowtolock and  status    free   The reason being  if I were to simply retrieve the row by ID  change the properties and then save  I could end up with two people accessing the same row simultaneously  This way  I simply send and update claiming this row as mine  then I try to retrieve the row which has the same properties I just updated with  If that row exists  great  If  for some reason it doesn t  someone else s  lock  command got there first   I simply return FALSE from my method   I do this by using context Database ExecuteSqlCommand which accepts a string command and an array of parameters   Just wanted to add this answer to point out that there will be scenarios in which retrieving a row  updating it  and saving it back to the DB won t suffice and that there are ways of running a straight update statement when necessary

User · Answer

Just modify one of the returned entities   Customer c    from x in dataBase Customers              where x Name     Test               select x  First    c Name    New Name   dataBase SaveChanges      Note  you can only update an entity  something that extends EntityObject  not something that you have projected using something like select new CustomObject Name   x Name

[c#] LINQ to Entities how to update a record

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