Prevent repeated http requests sent to NuGet repository when selecting a different page.

src/AddIns/Misc/PackageManagement/Project/Src/PackagesViewModel.cs

@@ -112,7 +112,7 @@ namespace ICSharpCode.PackageManagement
 		public void ReadPackages()
 		{
 			allPackages = null;
-			SelectedPageNumber = 1;
+			pages.SelectedPageNumber = 1;
 			UpdateRepositoryBeforeReadPackagesTaskStarts();
 			StartReadPackagesTask();
 		}
@@ -177,13 +177,9 @@ namespace ICSharpCode.PackageManagement
 
 		void UpdatePackagesForSelectedPage(PackagesForSelectedPageResult result)
 		{			
-			pages.CollectionChanged -= PagesChanged;
-			
 			pages.TotalItems = result.TotalPackages;
 			pages.TotalItemsOnSelectedPage = result.TotalPackagesOnPage;
 			UpdatePackageViewModels(result.Packages);
-			
-			pages.CollectionChanged += PagesChanged;
 		}
 		
 		void PagesChanged(object sender, NotifyCollectionChangedEventArgs e)
@@ -278,7 +274,13 @@ namespace ICSharpCode.PackageManagement
 		
 		public int SelectedPageNumber {
 			get { return pages.SelectedPageNumber; }
-			set { pages.SelectedPageNumber = value; }
+			set {
+				if (pages.SelectedPageNumber != value) {
+					pages.SelectedPageNumber = value;
+					StartReadPackagesTask();
+					base.OnPropertyChanged(null);
+				}
+			}
 		}
 		
 		public int PageSize {

src/AddIns/Misc/PackageManagement/Test/Src/Helpers/FakeTask.cs

@@ -11,19 +11,25 @@ namespace PackageManagement.Tests.Helpers
 		public bool IsStartCalled;
 		public bool IsCancelCalled;
 		
+		public bool RunTaskSynchronously;
+		
 		Func<TResult> function;
 		Action<ITask<TResult>> continueWith;
 		
-		public FakeTask(Func<TResult> function, Action<ITask<TResult>> continueWith)
+		public FakeTask(Func<TResult> function, Action<ITask<TResult>> continueWith, bool runTaskSynchronously)
 		{
 			this.function = function;
 			this.continueWith = continueWith;
+			RunTaskSynchronously = runTaskSynchronously;
 			Exception = new AggregateException(new Exception("FakeTaskAggregateInnerException"));
 		}
 		
 		public void Start()
 		{
 			IsStartCalled = true;
+			if (RunTaskSynchronously) {
+				ExecuteTaskCompletely();
+			}
 		}
 		
 		public TResult Result { get; set; }

src/AddIns/Misc/PackageManagement/Test/Src/Helpers/FakeTaskFactory.cs

@@ -11,6 +11,7 @@ namespace PackageManagement.Tests.Helpers
 	public class FakeTaskFactory : ITaskFactory
 	{
 		public bool IsCreateTaskCalled;
+		public bool RunTasksSynchronously;
 		
 		public FakeTask<PackagesForSelectedPageResult> FirstFakeTaskCreated { 
 			get { return FakeTasksCreated[0] as FakeTask<PackagesForSelectedPageResult>; }
@@ -23,7 +24,7 @@ namespace PackageManagement.Tests.Helpers
 			Action<ITask<TResult>> continueWith)
 		{
 			IsCreateTaskCalled = true;
-			var task = new FakeTask<TResult>(function, continueWith);
+			var task = new FakeTask<TResult>(function, continueWith, RunTasksSynchronously);
 			FakeTasksCreated.Add(task);
 			return task;
 		}

src/AddIns/Misc/PackageManagement/Test/Src/PackagesViewModelTests.cs

@@ -508,7 +508,7 @@ namespace PackageManagement.Tests
 		}
 		
 		[Test]
-		public void ReadPackages_CalledThreeTimesAndThenSelectedPageChanged_ViewModelPropertiesChangedEventFiresFourTimesWhenSelectedPageChanged()
+		public void ReadPackages_CalledThreeTimesAndThenSelectedPageChanged_ViewModelPropertiesChangedEventFiresOnceWhenSelectedPageChanged()
 		{
 			CreateViewModel();
 			viewModel.PageSize = 3;
@@ -527,16 +527,7 @@ namespace PackageManagement.Tests
 			viewModel.PropertyChanged += (sender, e) => count++;
 			viewModel.SelectedPageNumber = 2;
 			
-			// PropertyChanged fired for clearing the pages. 
+			Assert.AreEqual(1, count);
-			int propertyChangedEventFiredForClearingPagesCount = 1;
-			
-			// PropertyChanged fired once for each page.
-			int propertyChangedEventFiredForAddingPagesCount = 2;
-			
-			int totalExpectedPropertyChangedFiredCount =
-				propertyChangedEventFiredForClearingPagesCount + propertyChangedEventFiredForAddingPagesCount;
-			
-			Assert.AreEqual(totalExpectedPropertyChangedFiredCount, count);
 		}
 		
 		[Test]
@@ -1141,5 +1132,68 @@ namespace PackageManagement.Tests
 			
 			PackageCollectionAssert.AreEqual(expectedPackages, viewModel.PackageViewModels);
 		}
+		
+		[Test]
+		public void SelectedPageNumber_SixPackagesAndPageSizeIsFiveAndSelectedPageNumberIsChangedToTwo_OneReadPackagesTaskCreated()
+		{
+			CreateViewModel();
+			viewModel.PageSize = 5;
+			viewModel.AddSixFakePackages();
+			viewModel.ReadPackages();
+			CompleteReadPackagesTask();
+			ClearReadPackagesTasks();
+			
+			viewModel.SelectedPageNumber = 2;
+			
+			Assert.AreEqual(1, taskFactory.FakeTasksCreated.Count);
+		}
+		
+		[Test]
+		public void SelectedPageNumber_SixPackagesAndSelectedPageNumberIsSetToPageOneButUnchanged_NoReadPackagesTaskCreated()
+		{
+			CreateViewModel();
+			viewModel.PageSize = 5;
+			viewModel.AddSixFakePackages();
+			viewModel.ReadPackages();
+			CompleteReadPackagesTask();
+			ClearReadPackagesTasks();
+			
+			viewModel.SelectedPageNumber = 1;
+			
+			Assert.AreEqual(0, taskFactory.FakeTasksCreated.Count);
+		}
+		
+		[Test]
+		public void SelectedPageNumber_SixPackagesAndPageSizeIsFiveAndSelectedPageNumberIsChangedToTwo_PropertyChangedEventFiredAfterSelectedPageNumberChanged()
+		{
+			CreateViewModel();
+			viewModel.PageSize = 5;
+			viewModel.AddSixFakePackages();
+			viewModel.ReadPackages();
+			CompleteReadPackagesTask();
+			ClearReadPackagesTasks();
+			
+			int selectedPageNumber = 0;
+			viewModel.PropertyChanged += (source, e) => selectedPageNumber = viewModel.SelectedPageNumber;
+			viewModel.SelectedPageNumber = 2;
+			
+			Assert.AreEqual(2, selectedPageNumber);
+		}
+		
+		[Test]
+		public void SelectedPageNumber_SixPackagesAndPageSizeIsFiveAndSelectedPageNumberIsChangedToTwo_SelectedPageNumberChangedBeforeReadPackagesTaskStarted()
+		{
+			CreateViewModel();
+			viewModel.PageSize = 5;
+			viewModel.AddSixFakePackages();
+			viewModel.ReadPackages();
+			CompleteReadPackagesTask();
+			ClearReadPackagesTasks();
+			
+			taskFactory.RunTasksSynchronously = true;
+			viewModel.SelectedPageNumber = 2;
+			
+			Assert.AreEqual(1, viewModel.PackageViewModels.Count);
+		}
 	}
 }