When should I dispose of a data context

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It actually doesn’t matter too much. I asked Matt Warren from the LINQ to SQL team about this a while ago, and here’s the reply:

There are a few reasons we implemented
IDisposable:

If application logic needs to hold
onto an entity beyond when the
DataContext is expected to be used or
valid you can enforce that contract by
calling Dispose. Deferred loaders in
that entity will still be referencing
the DataContext and will try to use it
if any code attempts to navigate the
deferred properties. These attempts
will fail. Dispose also forces the
DataContext to dump its cache of
materialized entities so that a single
cached entity will not accidentally
keep alive all entities materialized
through that DataContext, which would
otherwise cause what appears to be a
memory leak.

The logic that automatically closes
the DataContext connection can be
tricked into leaving the connection
open. The DataContext relies on the
application code enumerating all
results of a query since getting to
the end of a resultset triggers the
connection to close. If the
application uses IEnumerable’s
MoveNext method instead of a foreach
statement in C# or VB, you can exit
the enumeration prematurely. If your
application experiences problems with
connections not closing and you
suspect the automatic closing behavior
is not working you can use the Dispose
pattern as a work around.

But basically you don’t really need to dispose of them in most cases – and that’s by design. I personally prefer to do so anyway, as it’s easier to follow the rule of “dispose of everything which implements IDisposable” than to remember a load of exceptions to it – but you’re unlikely to leak a resource if you do forget to dispose of it.

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