Fix premature disposal of IProgressMonitor in parallel background search.

This was the cause of "InvalidOperationException: The LinkedList node does not belong to current LinkedList." in ProgressCollector.UnregisterNamedMonitor().

Author: dgrunwald

src/AddIns/Misc/SearchAndReplace/Project/Engine/SearchManager.cs

@@ -28,6 +28,14 @@ namespace SearchAndReplace
 	public class SearchManager
 	{
 		#region FindAll
+		/// <summary>
+		/// Prepares a parallel search operation.
+		/// </summary>
+		/// <param name="strategy">The search strategy. Contains the search term and options.</param>
+		/// <param name="location">The location to search in.</param>
+		/// <param name="progressMonitor">The progress monitor used to report progress.
+		/// The parallel search operation will take ownership of this monitor: the monitor is disposed when the search finishes!</param>
+		/// <returns>Observable that starts performing the search when subscribed to. Does not support more than one subscriber!</returns>
 		public static IObservable<SearchedFile> FindAllParallel(ISearchStrategy strategy, SearchLocation location, IProgressMonitor progressMonitor)
 		{
 			currentSearchRegion = null;
@@ -122,7 +130,7 @@ public IDisposable Subscribe(IObserver<SearchedFile> observer)
 							observer.OnError(t.Exception);
 						else
 							observer.OnCompleted();
-						this.Dispose();
+						monitor.Dispose();
 					});
 				return this;
 			}
@@ -181,8 +189,9 @@ void ThrowIfCancellationRequested()
 
 			public void Dispose()
 			{
+				// Warning: Dispose() may be called concurrently while the operation is still in progress.
+				// We cannot dispose the progress monitor here because it is still in use by the search operation.
 				cts.Cancel();
-				monitor.Dispose();
 			}
 
 			SearchedFile SearchFile(FileName fileName)
@@ -509,6 +518,12 @@ public static bool IsResultSelected(SearchResultMatch result)
 				&& result.Length == editor.SelectionLength;
 		}
 
+		/// <summary>
+		/// Shows searchs results in the search results pad, and brings that pad to front.
+		/// </summary>
+		/// <param name="pattern">The pattern that is being searched for; used for the title of the search in the list of past searched.</param>
+		/// <param name="results">An observable that represents a background search operation.
+		/// The search results pad will subscribe to this observable in order to receive the search results.</param>
 		public static void ShowSearchResults(string pattern, IObservable<SearchedFile> results)
 		{
 			string title = StringParser.Parse("${res:MainWindow.Windows.SearchResultPanel.OccurrencesOf}",

src/Main/Base/Project/Editor/Search/ISearchResultFactory.cs

@@ -12,8 +12,18 @@ namespace ICSharpCode.SharpDevelop.Editor.Search
 	/// </summary>
 	public interface ISearchResultFactory
 	{
+		/// <summary>
+		/// Creates an <see cref="ISearchResult"/> object from a list of matches.
+		/// </summary>
+		/// <param name="title">The title of the search.</param>
+		/// <param name="matches">The list of matches. CreateSearchResult() will enumerate once through the IEnumerable in order to retrieve the search results.</param>
 		ISearchResult CreateSearchResult(string title, IEnumerable<SearchResultMatch> matches);
 
+		/// <summary>
+		/// Creates an <see cref="ISearchResult"/> object for a background search operation.
+		/// </summary>
+		/// <param name="title">The title of the search.</param>
+		/// <param name="matches">The background search operation. CreateSearchResult() will subscribe to the observable in order to retrieve the search results.</param>
 		ISearchResult CreateSearchResult(string title, IObservable<SearchedFile> matches);
 	}
 }

src/Main/Base/Project/Editor/Search/SearchResultsPad.cs

@@ -78,6 +78,10 @@ public void ClearLastSearchesList()
 			SD.WinForms.SetContent(contentPlaceholder, null);
 		}
 
+		/// <summary>
+		/// Shows a search in the search results pad.
+		/// The previously shown search will be stored in the list of past searches.
+		/// </summary>
 		public void ShowSearchResults(ISearchResult result)
 		{
 			if (result == null)
@@ -108,18 +112,31 @@ public void ShowSearchResults(ISearchResult result)
 			SearchResultsShown(this, EventArgs.Empty);
 		}
 
+		/// <summary>
+		/// Shows a search in the search results pad.
+		/// The previously shown search will be stored in the list of past searches.
+		/// </summary>
+		/// <param name="title">The title of the search.</param>
+		/// <param name="matches">The list of matches. ShowSearchResults() will enumerate once through the IEnumerable in order to retrieve the search results.</param>
 		public void ShowSearchResults(string title, IEnumerable<SearchResultMatch> matches)
 		{
 			ShowSearchResults(CreateSearchResult(title, matches));
 		}
 
+		/// <summary>
+		/// Performs a background search in the search results pad.
+		/// The previously shown search will be stored in the list of past searches.
+		/// </summary>
+		/// <param name="title">The title of the search.</param>
+		/// <param name="matches">The background search operation. ShowSearchResults() will subscribe to the observable in order to retrieve the search results.</param>
 		public void ShowSearchResults(string title, IObservable<SearchedFile> matches)
 		{
 			ShowSearchResults(CreateSearchResult(title, matches));
 		}
 
 		public event EventHandler SearchResultsShown = delegate {};
 
+		/// <inheritdoc cref="ISearchResultFactory.CreateSearchResult(string,IEnumerable{SearchResultMatch})"/>
 		public static ISearchResult CreateSearchResult(string title, IEnumerable<SearchResultMatch> matches)
 		{
 			if (title == null)
@@ -135,6 +152,7 @@ public static ISearchResult CreateSearchResult(string title, IEnumerable<SearchR
 		}
 
 
+		/// <inheritdoc cref="ISearchResultFactory.CreateSearchResult(string,IObservable{SearchResultMatch})"/>
 		public static ISearchResult CreateSearchResult(string title, IObservable<SearchedFile> matches)
 		{
 			if (title == null)

src/Main/Base/Project/Util/IProgressMonitor.cs

@@ -39,7 +39,7 @@ public interface IProgressMonitor : IDisposable, IProgress<double>
 		/// </summary>
 		/// <param name="workAmount">The amount of work this sub-task performs in relation to the work of this task.
 		/// That means, this parameter is used as a scaling factor for work performed within the subtask.</param>
-		/// <param name="childCancellationToken">
+		/// <param name="cancellationToken">
 		/// A cancellation token that can be used to cancel the sub-task.
 		/// Note: cancelling the main task will not cancel the sub-task.
 		/// </param>

src/Main/Base/Project/Util/ProgressCollector.cs

@@ -191,6 +191,9 @@ void UnregisterNamedMonitor(LinkedListNode<string> nameEntry)
 		{
 			lock (namedMonitors) {
 				bool wasFirst = namedMonitors.First == nameEntry;
+				// Note: if Remove() crashes with "InvalidOperationException: The LinkedList node does not belong to current LinkedList.",
+				// that's an indication that the progress monitor is being disposed multiple times concurrently.
+				// (which is not allowed according to IProgressMonitor thread-safety documentation)
 				namedMonitors.Remove(nameEntry);
 				if (wasFirst)
 					SetTaskName(namedMonitors.First != null ? namedMonitors.First.Value : null);