Hello,

I would like to follow up with the following Knowledge Base article which gives some tips how the performance can be improved: https://docs.telerik.com/devtools/winforms/knowledge-base/improve-filedialogs-performance 

I believe that it would be helpful.

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik

Hello, Curtis, 

I can confirm that on some devices, mostly touch devices, our file dialogs may load slowly. Could you please specify on what device exactly you are using the file dialogs?

I have logged it in our feedback portal by making this thread public on your behalf. You can track its progress, subscribe for status changes and add your comments on the following link - feedback item.

I have also updated your Telerik points.

I would like to note that all file dialogs are loading all directories and sub-directories of the predefined InitialDirectory and also all folders and their sub-folders that are visible on the MainNavigationTreeView on the left side. When a directory is loaded, the file dialogs are creating a DirectoryInfoWrapper object which subscribes for the Created, Changed, Renamed and Deleted events for this directory. This is the most time-consuming operation when loading the dialogs. A possible solution is to create a custom dialogs, which are not tracking the Created, Changed, Renamed and Deleted file and folder events. The performance on my side improved with 30-50%. Here is the code sample: 

    Public Class MyOpenFolderDialog
        Inherits RadOpenFolderDialog
        Protected Overrides Function CreateFileDialogForm() As FileDialogFormBase
            Return New MyOpenFolderDialogForm()
        End Function
    End Class

    Public Class MyOpenFolderDialogForm
        Inherits RadOpenFolderDialogForm
        Protected Overrides Function ShowDialogCore(Optional ByVal owner As IWin32Window = Nothing, Optional ByVal addWatcher As Boolean = True) As DialogResult
            addWatcher = False
            Return MyBase.ShowDialogCore(owner, addWatcher)
        End Function
    End Class

    Public Class MyOpenFileDialog
        Inherits RadOpenFileDialog

        Protected Overrides Function CreateFileDialogForm() As FileDialogFormBase
            Return New MyOpenFileDialogForm()
        End Function
    End Class

    Public Class MyOpenFileDialogForm
        Inherits RadOpenFileDialogForm

        Protected Overrides Function ShowDialogCore(Optional ByVal owner As IWin32Window = Nothing, Optional ByVal addWatcher As Boolean = True) As DialogResult
            addWatcher = False
            Return MyBase.ShowDialogCore(owner, addWatcher)
        End Function
    End Class

You can also skip a directory from being loaded in the file dialogs by cancelling the DirectoryRequesting event. Another hint to improve the loading time is to set the ShowNetworkLocations property to false. Its value indicates whether the dialog shows network computers in the navigation tree.

Additionally, when all directories are being traversed multiple exceptions like UnauthorizedAccessException, can occur. They are also consuming large amounts of time. You can track them by subscribing to the ExceptionRaised event of RadOpenFileDialog.

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik