var portal = ArcGISPortalManager.Current.GetActivePortal();
var owner = portal.GetSignOnUsername();
var userContent = await portal.GetUserContentAsync(owner);
//Get content for a specific folder (identified by its folder id)
//var userContent = await portal.GetUserContentAsync(owner, folderId);
//Get all the folders
foreach (var pf in userContent.PortalFolders)
{
//Do something with the folders
}
//Get all the content items
foreach (var pi in userContent.PortalItems)
{
//Do something with the portal items
}