WPF – Limit OpenFileDialog folder tree to a certain folder

Starting with .NET 8, you can constrain the OpenFileDialog and OpenFolderDialog folder tree to a given root folder. You can do so by setting the RootDirectory property on the dialog before calling ShowDialog().

It’s very important to note that this does not limit the selection and the navbar navigation in any way. The user will still be able to navigate to folders outside the specified RootDirectory. The same goes for the InitialDirectory property which you can set to any folder you’d like outside the RootDirectory.

Let’s look at an example:

var dialog = new OpenFileDialog
{
    InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments),
    RootDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures),
};

dialog.ShowDialog();

This will show an open file dialog focused on the MyDocuments folder, while its folder tree on the left will be scoped to the specified root directory – in this case, MyPictures.