System.InvalidCastException was unhandled
  Message="Unable to cast object of type 'HtmlAgilityPack.HtmlNode' to type 'Editor.SteelArrow.Tags.SASet'."
  Source="Editor"
  StackTrace:
       at Editor.SteelArrow.DatasourceManager.get_Sources() in C:\Work\Tests\Editor\Editor\SteelArrow\DatasourceManager.cs:line 72
       at Editor.SteelArrow.DatasourceManager.project_ProjectLoaded(Object sender, EventArgs e) in C:\Work\Tests\Editor\Editor\SteelArrow\DatasourceManager.cs:line 34
       at System.EventHandler.Invoke(Object sender, EventArgs e)
       at Editor.Project.OnProjectLoadedHandler() in C:\Work\Tests\Editor\Editor\Project.cs:line 55
       at Editor.Project.set_ProjectDirectory(String value) in C:\Work\Tests\Editor\Editor\Project.cs:line 40
       at Editor.FormMain.menuOpenDirectory_Click(Object sender, EventArgs e) in C:\Work\Tests\Editor\Editor\FormMain.cs:line 48
       at System.Windows.Forms.ToolStripItem.RaiseEvent(Object key, EventArgs e)
       at System.Windows.Forms.ToolStripMenuItem.OnClick(EventArgs e)
       at System.Windows.Forms.ToolStripItem.HandleClick(EventArgs e)
       at System.Windows.Forms.ToolStripItem.HandleMouseUp(MouseEventArgs e)
       at System.Windows.Forms.ToolStripItem.FireEventInteractive(EventArgs e, ToolStripItemEventType met)
       at System.Windows.Forms.ToolStripItem.FireEvent(EventArgs e, ToolStripItemEventType met)
       at System.Windows.Forms.ToolStrip.OnMouseUp(MouseEventArgs mea)
       at System.Windows.Forms.ToolStripDropDown.OnMouseUp(MouseEventArgs mea)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
       at System.Windows.Forms.ToolStrip.WndProc(Message& m)
       at System.Windows.Forms.ToolStripDropDown.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at Editor.Program.Main() in C:\Work\Tests\Editor\Editor\Program.cs:line 17
       at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()