asked on
LinqToSQL Update
I'm using the code below to update a record in a SQLCE database. It seems strange that I have to fetch the record before I update it ?
How would I update multiple records like in SQL.
(I hope that the answer is not what I'm suspecting!)
Using db = New sContext(ConnectionString)
'find record
Dim q = From s In db.Spots _
Where s.sId = iId _
Select s
If q.Count() = 1 Then
Dim sp As SpotClass = (From s In db.Spots _
Where s.sId = iId _
Select s).First()
sp.sActive = "False"
sp.sEndDate = DateTime.Now.ToUniversalTime
db.SubmitChanges()
End If
How would I update multiple records like in SQL.
UPDATE TBLTASK SET COMPLETEDATE = NOW WHERE TASKTYPE = 'AUTO'
(I hope that the answer is not what I'm suspecting!)
.NET Programming
Last Comment
Craig Wagner
ASKER CERTIFIED SOLUTION
THIS SOLUTION ONLY AVAILABLE TO MEMBERS.
View this solution by signing up for a free trial.
Members can start a 7-Day free trial and enjoy unlimited access to the platform.
LINQ-to-SQL (and Entity Framework) are designed to work on one entity at a time. If you've got a form where you are presenting a single instance of an object, letting the user change the values, and then pushing those changes to the database it works very well. It even works well if you've got a list of objects because the DataContext (or ObjectContext in EF) will track which objects and which columns have changed an only issue the necessary SQL.
However, if you want to do a bulk operation (e.g. update all rows that meet certain criteria, delete all rows that meet certain criteria) then LINQ-to-SQL and EF are the wrong tools. You could use them by retrieving a set containing all the objects you want to update, looping through the set and changing each one, then issuing SubmitChanges. The problems with that are that a SQL UPDATE will be issued for each changed object, so if you've got hundreds (or thousands) of objects that meet the criteria it will be incredibly inefficient vs. a single UPDATE statement and each UPDATE is performed in its own transaction instead of a single larger transaction.
However, if you want to do a bulk operation (e.g. update all rows that meet certain criteria, delete all rows that meet certain criteria) then LINQ-to-SQL and EF are the wrong tools. You could use them by retrieving a set containing all the objects you want to update, looping through the set and changing each one, then issuing SubmitChanges. The problems with that are that a SQL UPDATE will be issued for each changed object, so if you've got hundreds (or thousands) of objects that meet the criteria it will be incredibly inefficient vs. a single UPDATE statement and each UPDATE is performed in its own transaction instead of a single larger transaction.
ASKER
Can I use it to send DDL commands ?
I'm not sure. In theory it should work if you sent a DDL statement through ExecuteCommand but it would probably be quicker just to throw a test together and try it. You've already got the DataContext and everything set up, it should only take a minute to try something simple. It's also getting beyond the scope of the original question.
Why would anyone use the chunk of code that I posted then ?
Can I use this with DDL ?