Dataset copy() memory leak

Question

Hi

I have an application that needs to frequently backup a dataset and revert to that backup if the users decides to cancel an action.

There is a global dataset created at the top of the class:

DataSet database = null;

Every time a form is opened the main dataset is copied into the created variable:

database = AppModel.Instance.Data.Data.Copy();

The problem is that every time the form is opened the memory increases by quite a lot and is never released.

I've tried disposing the database variable after it's been used but the memory still remains high - This has left me to believe that the DataSet.Copy() method allocates to new memory every time.

Any suggestions to free up the memory would be greatly appreciated.

Regards,

Jason

Vulpes · Answer

It looks as though something is still holding onto a reference to the original DataSet object or one of its constituent DataTables which is preventing it from being GC'ed. Are you binding to it at all?

Jason Nesbitt · Answer

Still no luck. We changed the cancel action to do this (The copiedDataSet was made from the originalDataSet just before the form opens): originalDataSet.Dispose(); originalDataSet = null; originalDataSet = copiedDataSet; copiedDataSet.Dispose(); copiedDataSet = null; GC.Collect(); It occasionally works the first time but doesn't on all of the other times. The memory still increases and isn't released. Cheers Jason

Vulpes · Answer

Just going back to first principles for a moment (which sometimes helps) the DataSet.Copy method will copy the DataSet on which it's called to a new DataSet object. The original object won't be garbage collected unless there are no longer any references to it and even then there might be a delay before the memory is released. So could you be hanging on to a reference to the original DataSet somewhere? If so then you need to set it to null after calling Dispose(). If you don't think this is happening or it's a very large DataSet then you could try calling GC.Collect() after the copying operation to force an immediate garbage collection.

Jason Nesbitt · Answer

Thanks for the quick reply. Sadly it didn't work. The variable is declared as static globally so there is definitely only one instance of it but the DataSet.Copy() method still increases the memory every time the DataSet is copied to it.

Vulpes · Answer

If you declare the variable as static then that will ensure that there's only ever one copy: static DataSet database = null;