Fixed thread-safety issue in DefaultProjectContent (possible cause of crash #495)

src/Main/ICSharpCode.SharpDevelop.Dom/Project/Src/ProjectContent/DefaultProjectContent.cs

@@ -711,11 +711,13 @@ namespace ICSharpCode.SharpDevelop.Dom
 					}
 				}
 			}
+			lock (namespaces) {
 				Dictionary<string, NamespaceStruct> dict = GetNamespaces(language);
 				foreach (var namespaceStruct in dict.Values) {
 					AddNamespaceStructContents(list, namespaceStruct, language, lookInReferences);
 				}
 			}
+		}
 		
 		/// <summary>
 		/// Adds the contents of the specified <paramref name="nameSpace"/> to the <paramref name="list"/>.
@@ -735,12 +737,14 @@ namespace ICSharpCode.SharpDevelop.Dom
 				}
 			}
 			
+			lock (namespaces) {
 				Dictionary<string, NamespaceStruct> dict = GetNamespaces(language);
 				if (dict.ContainsKey(nameSpace)) {
 					NamespaceStruct ns = dict[nameSpace];
 					AddNamespaceStructContents(list, ns, language, lookInReferences);
 				}
 			}
+		}
 
 		void AddNamespaceStructContents(List<ICompletionEntry> list, NamespaceStruct ns, LanguageProperties language, bool lookInReferences)
 		{
@@ -812,8 +816,10 @@ namespace ICSharpCode.SharpDevelop.Dom
 				}
 			}
 			
+			lock (namespaces) {
 				return GetNamespaces(language).ContainsKey(name);
 			}
+		}
 		
 		bool MatchesRequest(SearchTypeRequest request, ref SearchTypeResult result)
 		{