Comments on: Discard changes in LINQ to SQL DataContext

By: Graeme

Graeme — Mon, 28 Jun 2010 15:24:59 +0000

The only reason I can think of that would cause that line to fail in C# is that you need to have parenthesis at the end of the GetType function. Here’s my conversion of that function. Sorry, the formatting will be all screwy.

public void DiscardInsertsAndDeletes(DataContext data)
{
var changes = data.GetChangeSet();

foreach (var insertion in changes.Inserts)
{
data.GetTable(insertion.GetType()).DeleteOnSubmit(insertion);
}

foreach (var deletion in changes.Deletes)
{
data.GetTable(deletion.GetType()).InsertOnSubmit(deletion);
}
}

By: Scott

Scott — Mon, 28 Jun 2010 06:45:49 +0000

Can anyone convert the DiscardInsertsAndDeletes() and DiscardUpdates() methods to C#? I can’t get data.GetTable(insertion.GetType).DeleteOnSubmit(insertion)
to work properly. Thank you.

By: John Svercek

John Svercek — Thu, 01 Apr 2010 03:35:27 +0000

WOW, thanks this is great. I was just getting ready to go back to ADO. Saved me a ton of work.

By: Donnie Wishard

Donnie Wishard — Tue, 30 Mar 2010 20:57:52 +0000

Thanks for this, exactly what I needed. Saved me a great deal of time!

By: Kevin

Kevin — Fri, 26 Mar 2010 15:11:52 +0000

Exactly what I was looking for… Great Job and Thank You!!!

By: Derin

Derin — Thu, 25 Feb 2010 12:39:18 +0000

Thanks Graemehill,

I searched a lot find a solution to discard all changes, now i got.

it was really helpful

thanks

By: macias

macias — Wed, 10 Feb 2010 12:47:48 +0000

Unfortunately I found problem with discard along with transactions. Please take a look:

begin trans
insert
update (of inserted record)
*
commit trans

in case of failure, all changes should be discarded.

However since all actions are inside transaction, on failure the insert is rolled back, and there is no way to fetch the data back to record to discard update. As the result of DiscardChanges I get exception from Linq about non existing record.

I can make a workaround for this particular case, but it would be great if someone had an idea for general, smart solution.

By: macias

macias — Fri, 29 Jan 2010 11:52:47 +0000

Thank you very much for explanation. I have still problems with inserts though. Normally I work like this:
record = new Record();
db.Table.InsertOnSubmit(record);

// here setting all the values of the record

// here discard may occur (+jump off the procedure)

and despite the loop iterates through this table it does not discard changes.

As a workaround I introduced new bool value which tracks if this is new record or just edit, and just before submit I add

// here discard may occur (+jump off the procedure)
if (is_insert)
db.Table.InsertOnSubmit(record);

This works, but thanks to not using discarding inserts.

By: Graeme

Graeme — Tue, 26 Jan 2010 17:50:41 +0000

Refresh() just reverts the properties on an entity to their original state based on values in the database. Basically, it is an operation on the entities that you pass in the parameter, not on the DataContext. The result is that it will update entity properties, but not necessarily that entity’s state in the DataContext.

If encapsulation is what you’re worried about, just make a functions that calls DiscardInsertsAndDeletes and DiscardUpdates.

By: macias

macias — Tue, 26 Jan 2010 10:06:36 +0000

Thank you for useful post — one question though. Why the same method with refresh does not work for inserts? I.e. I would like to make the discarding procedure uniform for all three types, so I thought the best pick would be to refresh all tables — altered by delete, insert or update.