i completely misunderstood how linq deferred execution worked... i'm surprised the whole thing didn't blow up with dozens of Gtk-CRITICALs every time you modified the watchlist 0uo

MainWindow.cs

@@ -54,8 +54,36 @@ namespace Buypeeb {
 
 		static SemaphoreSlim taskLimit = new SemaphoreSlim(6);
 		private Queue<string> updateQueue = new Queue<string>();
-		private IEnumerable<YahooAuctionsItem> filterQuery;
+		private IEnumerable<YahooAuctionsItem> filterQuery {
-		private IEnumerable<YahooAuctionsItem> outdatedItemQuery;
+			get {
+				// father forgive me for i have lynned
+				return
+					from item in this.settings.watchlist.Values.ToList()
+					where (item.favourite != this.filterChecks["Favourites"].Active ||
+					item.favourite == this.filterChecks["NonFavourites"].Active) &&
+					(item.available != this.filterChecks["Active"].Active ||
+					item.available == this.filterChecks["Ended"].Active) &&
+					(item.endingToday != this.filterChecks["EndingToday"].Active ||
+					item.endingToday == this.filterChecks["EndingAfterToday"].Active) &&
+					(item.hasWinPrice != this.filterChecks["WithWinPrice"].Active ||
+					item.hasWinPrice == this.filterChecks["WithNoWinPrice"].Active) &&
+					(String.IsNullOrWhiteSpace(this.searchEntry.Text) ||
+					item.name.ToLower().Contains(this.searchEntry.Text.ToLower()) ||
+					item.originalName.ToLower().Contains(this.searchEntry.Text.ToLower()))
+					select item;
+			}
+		}
+		private IEnumerable<YahooAuctionsItem> outdatedItemQuery {
+			get {
+				// only returns items that meet all of the following:
+				// - marked as "ready", as in, they aren't in the process of updating
+				// - not updated since the interval
+				return
+				from item in this.settings.watchlist.Values.ToList()
+				where item.ready && this.settings.ItemNotUpdatedSinceInterval(item)
+				select item;
+			}
+		}
 
 		private YahooAuctionsItem selectedItem {
 			get {
@@ -121,30 +149,6 @@ namespace Buypeeb {
 				this.filterChecks[name].Active = false;
 			}
 
-			// only returns items that meet all of the following:
-			// - marked as "ready", as in, they aren't in the process of updating
-			// - not updated since the interval
-			this.outdatedItemQuery =
-			from item in this.settings.watchlist.Values.ToList()
-			where item.ready && this.settings.ItemNotUpdatedSinceInterval(item)
-			select item;
-
-			// father forgive me for i have lynned
-			this.filterQuery =
-				from item in this.settings.watchlist.Values.ToList()
-				where (item.favourite != this.filterChecks["Favourites"].Active ||
-				item.favourite == this.filterChecks["NonFavourites"].Active) &&
-				(item.available != this.filterChecks["Active"].Active ||
-				item.available == this.filterChecks["Ended"].Active) &&
-				(item.endingToday != this.filterChecks["EndingToday"].Active ||
-				item.endingToday == this.filterChecks["EndingAfterToday"].Active) &&
-				(item.hasWinPrice != this.filterChecks["WithWinPrice"].Active ||
-				item.hasWinPrice == this.filterChecks["WithNoWinPrice"].Active) &&
-				(String.IsNullOrWhiteSpace(this.searchEntry.Text) ||
-				item.name.ToLower().Contains(this.searchEntry.Text.ToLower()) ||
-				item.originalName.ToLower().Contains(this.searchEntry.Text.ToLower()))
-				select item;
-
 			// bind treeview columns to watchlist instead of needing to manually sync its liststore
 			this.itemTreeView = (TreeView)builder.GetObject("TreeViewItems");
 			this.items = new ListStore(typeof(YahooAuctionsItem));
@@ -266,9 +270,9 @@ namespace Buypeeb {
 			}
 		}
 
-		private void UpdateItem(string id, bool evenIfAlreadyUpdating = false, bool force = false) {
+		private void UpdateItem(string id, bool refilterWhenDone = false) {
 			var item = this.settings.watchlist[id];
-			if (item.updatedRecently && !force) {
+			if (item.updatedRecently) {
 				// the item has been updated recently, and force is not true
 				return;
 			}
@@ -278,7 +282,13 @@ namespace Buypeeb {
 			taskLimit.Wait();
 			var t = Task.Factory.StartNew(() => {
 				this.UpdateThread(id);
-			}).ContinueWith(task => { taskLimit.Release(); });
+			}).ContinueWith(task => {
+				taskLimit.Release();
+				if (refilterWhenDone) {
+					var m = (TreeModelFilter)this.itemTreeView.Model;
+					m.Refilter();
+				}
+			});
 		}
 
 		private void UpdateItems() {
@@ -636,13 +646,30 @@ namespace Buypeeb {
 				}
 				catch (Exception e) {
 					Console.WriteLine(e);
-					MsgBox($"Failed to write {sd.Filename}!\n{e.Message}.", ButtonsType.Ok);
+					var md = MsgBox($"Failed to write {sd.Filename}!\n{e.Message}.", ButtonsType.Ok);
+					md.Run();
+					md.Dispose();
 				}
 			}
 
 			sd.Dispose();
 		}
 
+		private void ButtonHelpClicked(object sender, EventArgs args) {
+			Console.WriteLine("Watchlist:");
+			foreach (var item in this.settings.watchlist) {
+				Console.WriteLine(item);
+			}
+			Console.WriteLine("---\nFilter results:");
+			foreach (var item in this.filterQuery) {
+				Console.WriteLine(item);
+			}
+			Console.WriteLine("---\nListstore contents:");
+			foreach (object[] item in this.items) {
+				Console.WriteLine(item[0]);
+			}
+		}
+
 		private void ButtonQuitClicked(object sender, EventArgs a) {
 			var md = this.MsgBox("Are you sure you want to quit?");
 
@@ -846,6 +873,13 @@ namespace Buypeeb {
 
 		private bool ItemFilter(ITreeModel model, TreeIter iter) {
 			var item = (YahooAuctionsItem)model.GetValue(iter, 0);
+			if (item == null) {
+				return true;
+			}
+			if (item.price == 0) {
+				// the item has only just been added, so we can't compare it against the filters, since it's missing most of its data
+				return true;
+			}
 
 			bool Filtered(string name) {
 				return this.filterChecks[name].Active;

ui/main.glade

@@ -430,12 +430,12 @@
                     <child>
                       <object class="GtkToolButton">
                         <property name="visible">True</property>
-                        <property name="sensitive">False</property>
                         <property name="can_focus">False</property>
                         <property name="tooltip_text" translatable="yes">Help</property>
                         <property name="label" translatable="yes">Help</property>
                         <property name="use_underline">True</property>
                         <property name="stock_id">gtk-help</property>
+                        <signal name="clicked" handler="ButtonHelpClicked" swapped="no"/>
                         <accelerator key="slash" signal="clicked" modifiers="GDK_CONTROL_MASK"/>
                       </object>
                       <packing>