/// ///////////////////////////////////////////////////////////////
// Implementation
void request_page(int page_num)
{
if (page_num < 0)
{
throw new ArgumentOutOfRangeException();
}
if (!_dataRows.TryAdd(page_num, null)) // Return if the key already exists.
{
return;
}
ItemsEventArgs args = new ItemsEventArgs(
_pageSize * page_num, // startIndex
_pageSize, // requestedCount
SortDescriptions.FirstOrDefault());
Task <List <T> > items_task = ItemsRequest(this, args);
items_task.ContinueWith(task => {
_dataRows[page_num] = task.Result; // Dictionary<>はthread-safe ではない!
Console.WriteLine("Updated: " + page_num);
Action action = () => { this.Refresh(); };
Application.Current.Dispatcher.BeginInvoke(action); // UIスレッドに戻す
});
}
Task <List <DataRow> > OnItemsRequest(object sender, ItemsEventArgs arg2)
{
int startIndex = arg2.StartIndex;
int count = arg2.RequestedCount;
SortDescription sort = arg2.SortDescription;
var task = Task <List <DataRow> > .Run(() => {
List <DataRow> items = new List <DataRow>();
for (int i = startIndex; i < startIndex + count; i++)
{
DataRow row = dataTable.NewRow();
row[0] = i.ToString();
row[1] = rnd.Next(1000).ToString();
row[2] = rnd.Next(1000).ToString();
items.Add(row);
}
// Simulating heavy loading time
Thread.Sleep(2 * 1000);
return(items);
});
return(task);
}