dispose FileSystemWatcher in TP.Dispose() method

src/FsXaml.Wpf.TypeProvider/TypeProvider.Helper.fs

@@ -21,13 +21,14 @@ let optionType ty = typedefof<option<_>>.MakeGenericType[| ty |]
 
 /// Implements invalidation of schema when the file changes
 let watchForChanges (ownerType:TypeProviderForNamespaces) (fileName:string) = 
-    if fileName.StartsWith("http", System.StringComparison.InvariantCultureIgnoreCase) then () else
+    if fileName.StartsWith("http", System.StringComparison.InvariantCultureIgnoreCase) then None else
 
     let path = Path.GetDirectoryName(fileName)
     let name = Path.GetFileName(fileName)
     let watcher = new FileSystemWatcher(Filter = name, Path = path)
     watcher.Changed.Add(fun _ -> ownerType.Invalidate())
     watcher.EnableRaisingEvents <- true
+    Some (watcher :> IDisposable) 
 
 // Get the assembly and namespace used to house the provided types
 let thisAssembly = System.Reflection.Assembly.GetExecutingAssembly()

src/FsXaml.Wpf.TypeProvider/XamlTypeProvider.fs

@@ -227,7 +227,13 @@ type public XamlTypeProvider(config : TypeProviderConfig) as this =
     let assembly = Assembly.GetExecutingAssembly()
     let nameSpace = this.GetType().Namespace
     let providerType = ProvidedTypeDefinition(assembly, nameSpace, "XAML", Some typeof<obj>, IsErased = false)
-    let missingValue = "@@@missingValue###"
+    let fileSystemWatcher: IDisposable option ref = ref None
+
+    let disposeFileSystemWatcher() = 
+        !fileSystemWatcher |> Option.iter (fun x -> 
+            Diagnostics.Debug.WriteLine ("[FsXaml] Disposing FileSystemWatcher.")
+            x.Dispose()) 
+        fileSystemWatcher := None
 
     let assemblies = 
         config.ReferencedAssemblies 
@@ -260,21 +266,20 @@ type public XamlTypeProvider(config : TypeProviderConfig) as this =
             instantiationFunction = (fun typeName parameterValues ->   
                 let resourcePath = string parameterValues.[0]
                 let resolvedFileName = findConfigFile config.ResolutionFolder resourcePath
-                watchForChanges this resolvedFileName
+                disposeFileSystemWatcher()
+                Diagnostics.Debug.WriteLine ("[FsXaml] Creating FileSystemWatcher.")
+                fileSystemWatcher := watchForChanges this resolvedFileName
 
                 use reader = new StreamReader(resolvedFileName)                            
                 let elements = XamlTypeUtils.readElements schemaContext reader resolvedFileName
-
                 let root = List.head elements
 
-                let ucType = typeof<System.Windows.Controls.UserControl>
-
                 let outerType =
                     let createFactoryType factoryType =
                         let outertype = ProvidedTypeDefinition(assembly, nameSpace, typeName, Some(factoryType), IsErased = false)
                         let ctor = ProvidedConstructor([])
-                        ctor.BaseConstructorCall <- fun args -> factoryType.GetConstructors().[0], [Expr.Value(resourcePath)]
-                        ctor.InvokeCode <- fun args -> <@@ 0 @@>
+                        ctor.BaseConstructorCall <- fun _ -> factoryType.GetConstructors().[0], [Expr.Value(resourcePath)]
+                        ctor.InvokeCode <- fun _ -> <@@ 0 @@>
                         outertype.AddMember ctor
                         outertype
                     match root.NodeType with
@@ -298,5 +303,8 @@ type public XamlTypeProvider(config : TypeProviderConfig) as this =
 
         this.AddNamespace(nameSpace, [ providerType ])
 
+    interface IDisposable with
+        member __.Dispose() = disposeFileSystemWatcher()
+
 [<assembly:TypeProviderAssembly>] 
 do()