C#: BackgroundWorker cloning resources?
- by Dav
The problem
I've been struggling with this partiular problem for two days now and just run out of ideas. A little... background: we have a WinForms app that needs to access a database, construct a list of related in-memory objects from that data, and then display on a DataGridView. Important point is that we first populate an app-wide cache (List), and then create a mirror of the cache local to the form on which the DGV lives (using List constructor param).
Because fetching the data takes a good few seconds (DB sits on a LAN server) to load, we decided to use a BackgroundWorker, and only refresh the DGV once the data is loaded. However, it seems that doing the loading via a BGW results in some memory leak... or an error on my part. When loaded using a blocking method call, the app consumes about 30MB of RAM; with a BGW this jumps to 80MB! While it may not seem as much anyway, our clients are not too happy about it.
Relevant code
Form
private void MyForm_Load(object sender, EventArgs e)
{
MyRepository.Instance.FinishedEvent += RefreshCache;
}
private void RefreshCache(object sender, EventArgs e)
{
dgvProducts.DataSource = new List<MyDataObj>(MyRepository.Products);
}
Repository
private static List<MyDataObj> Products { get; set; }
public event EventHandler ProductsLoaded;
public void GetProductsSync()
{
List<MyDataObj> p;
using (MyL2SDb db = new MyL2SDb(MyConfig.ConnectionString))
{
p = db.PRODUCTS
.Select(p => new MyDataObj {Id = p.ID, Description = p.DESCR})
.ToList();
}
Products = p;
// tell the form to refresh UI
if (ProductsLoaded != null)
ProductsLoaded(this, null);
}
public void GetProductsAsync()
{
using (BackgroundWorker myWorker = new BackgroundWorker())
{
myWorker.DoWork += delegate
{
List<MyDataObj> p;
using (MyL2SDb db = new MyL2SDb(MyConfig.ConnectionString))
{
p = db.PRODUCTS
.Select(p => new MyDataObj {Id = p.ID, Description = p.DESCR})
.ToList();
}
Products = p;
};
// tell the form to refresh UI when finished
myWorker.RunWorkerCompleted += GetProductsCompleted;
myWorker.RunWorkerAsync();
}
}
private void GetProductsCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (ProductsLoaded != null)
ProductsLoaded(this, null);
}
End!
GetProductsSync or GetProductsAsync are called on the main thread, not shown above. Could it be that the GarbageCollector just gets lost with two threads? Or is it the task manager that shows incorrect values?
Will be greateful for any responses, suggestions, criticism.
