public void AddFilter( 
   BrowseProjectFilter filter
)

{
  BrowseProjectFilter portalAndLocalProjectsFilter = new();
  //A filter to pick projects from the portal
  //This filter will allow selection of ppkx and portal project items on the portal
  portalAndLocalProjectsFilter.AddFilter(BrowseProjectFilter.GetFilter("esri_browseDialogFilters_projects_online_proprojects"));
  //A filter to pick projects from the local machine
  portalAndLocalProjectsFilter.AddFilter(BrowseProjectFilter.GetFilter("esri_browseDialogFilters_projects"));
  //Create the OpenItemDialog and set the filter to the one we just created
  var openDlg = new OpenItemDialog()
  {
    Title = "Select a Project",
    MultiSelect = false,
    BrowseFilter = portalAndLocalProjectsFilter
  };
  //Show the dialog
  var result = openDlg.ShowDialog();
  //Check if the user clicked OK and selected an item
  bool? ok = openDlg.ShowDialog();
  if (!ok.HasValue || openDlg.Items.Count == 0)
    return; //nothing selected
  var selectedItem = openDlg.Items.FirstOrDefault();
  //Open the project use the OpenAsync method.
}