public class FolderConnectionProjectItem : ArcGIS.Desktop.Internal.Catalog.ProjectItemInfoCrawl, ArcGIS.Desktop.Core.IMetadata, ArcGIS.Desktop.Core.IProjectItem, ArcGIS.Desktop.Core.ISearchableItem, System.ComponentModel.INotifyPropertyChanged  

{
  // Get all the folder connections in a project
  IEnumerable<FolderConnectionProjectItem> projectFolders = Project.Current.GetItems<FolderConnectionProjectItem>();
  // use projectFolders;
}

{
  // Get all the items that can be accessed from a folder connection. The items immediately 
  // contained by a folder, that is, the folder's children, are returned including folders
  // and individual items that can be used in ArcGIS Pro. This method does not return all 
  // items contained by any sub-folder that can be accessed from the folder connection.
  FolderConnectionProjectItem folderConnection = Project.Current.GetItems<FolderConnectionProjectItem>()
                                                      .FirstOrDefault(folder => folder.Name.Equals("Data"));
  //Note: Needs QueuedTask to run
  IEnumerable<Item> folderContents = folderConnection.GetItems();
}

{
  // Remove a folder connection from a project; the folder stored on the local disk 
  // or the network is not deleted

  //Note: Needs QueuedTask to run
  {
    bool result = false;
    FolderConnectionProjectItem folderToRemove = Project.Current.GetItems<FolderConnectionProjectItem>()
      .FirstOrDefault(folder => folder.Name.Equals("Data"));
    if (folderToRemove != null)
      result = Project.Current.RemoveItem(folderToRemove as IProjectItem);
    // use result
  }
}

{
  //Gets all the folder connections in the current project
  var projectFolders = Project.Current.GetItems<FolderConnectionProjectItem>();
  foreach (var FolderItem in projectFolders)
  {
    //Do Something with the Folder connection.
  }
}

{
  FolderConnectionProjectItem folderProjItem = Project.Current.GetItems<FolderConnectionProjectItem>().FirstOrDefault(item => item.Name.Equals("myDataFolder"));
  // Use folderProjItem;
}

{
  // Remove a folder connection from a project; the folder stored on the local disk or the network is not deleted
  FolderConnectionProjectItem folderToRemove = Project.Current.GetItems<FolderConnectionProjectItem>().FirstOrDefault(myfolder => myfolder.Name.Equals("PlantSpecies"));
  if (folderToRemove != null)
    Project.Current.RemoveItem(folderToRemove as IProjectItem);
}

{
  List<Item> _mxd = [];
  //Gets all the folder connections in the current project
  var allFoldersItem = Project.Current.GetItems<FolderConnectionProjectItem>();
  if (allFoldersItem != null)
  {
    //iterate through all the FolderConnectionProjectItems found
    foreach (var folderItem in allFoldersItem)
    {
      //Search for mxd files in that folder connection and add it to the List<T>
      //Note:ArcGIS Pro automatically creates and dynamically updates a searchable index as you build and work with projects. 
      //Items are indexed when they are added to a project.
      //The first time a folder or database is indexed, indexing may take a while if it contains a large number of items. 
      //While the index is being created, searches will not return any results.
      _mxd.AddRange(folderItem.GetItems());
    }
  }
}

{
  var contentItem = Project.Current.GetItems<FolderConnectionProjectItem>().First();
  //Check if the MCT is required for Refresh()
  if (contentItem.IsMainThreadRequired)
  {
    // Note: Needs QueuedTask to run
    contentItem.Refresh();
  }
  else
  {
    //if item.IsMainThreadRequired returns false, any
    //thread can be used to invoke Refresh(), though
    //BackgroundTask is preferred.
    contentItem.Refresh();

    //Or, via BackgroundTask
    ArcGIS.Core.Threading.Tasks.BackgroundTask.Run(() =>
      contentItem.Refresh(), ArcGIS.Core.Threading.Tasks.BackgroundProgressor.None);
  }
}

{
  //GetItems searches project content
  var map = Project.Current.GetItems<MapProjectItem>().FirstOrDefault(m => m.Name == "Map1");
  var layout = Project.Current.GetItems<LayoutProjectItem>().FirstOrDefault(m => m.Name == "Layout1");
  var folders = Project.Current.GetItems<FolderConnectionProjectItem>();
  var style = Project.Current.GetItems<StyleProjectItem>().FirstOrDefault(s => s.Name == "ArcGIS 3D");

  //Find item uses a catalog path. The path can be to a file or dataset
  var fcPath = @"C:\Pro\CommunitySampleData\Interacting with Maps\Interacting with Maps.gdb\Crimes";
  var pdfPath = @"C:\Temp\Layout1.pdf";
  var imgPath = @"C:\Temp\AddinDesktop16.png";

  var fc = Project.Current.FindItem(fcPath);
  var pdf = Project.Current.FindItem(pdfPath);
  var img = Project.Current.FindItem(imgPath);
}