Fix deletion of unmanaged files

[HebaruSan]

Problem

If you open the Unmanaged Files tab from #3833 and try to delete a file, an exception is thrown:

System.IO.IOException: The directory name is invalid.

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileSystemEnumerableIterator`1.CommonInit()
   at System.IO.FileSystemEnumerableIterator`1..ctor(String path, String originalUserPath, String searchPattern, SearchOption searchOption, SearchResultHandler`1 resultHandler, Boolean checkHost)
   at System.IO.Directory.EnumerateFileSystemEntries(String path, String searchPattern, SearchOption searchOption)
   at CKAN.GameInstance.HasManagedFiles(Registry registry, String absPath)
   at CKAN.GUI.UnmanagedFiles.DeleteButton_Click(Object sender, EventArgs e)
   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.ToolStrip.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.ToolStrip.WndProc(Message& m)
   at System.Windows.Forms.MenuStrip.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

(Deleting a directory works fine.)

Cause

GameInstance.HasManagedFiles is passing its parameter to Directory.EnumerateFileSystemEntries even if it's a file. Directory.EnumerateFileSystemEntries hates that.

Changes

• Now GameInstance.HasManagedFiles only calls Directory.EnumerateFileSystemEntries if the given path exists and is a directory.
• While fixing this I realized that File.Delete and Directory.Delete might throw exceptions if the user doesn't have access to the file. Now these will be caught and displayed.

[techman83]

Looks great, this gave me a right chuckle!

GameInstance.HasManagedFiles is passing its parameter to Directory.EnumerateFileSystemEntries even if it's a file. Directory.EnumerateFileSystemEntries hates that.