public UploadDefinition( 
   string portalURL,
   Item itemToUpload,
   string[] tags
)

{
  // Create the item to be uploaded, based on a local file
  var itemToUpload = ItemFactory.Instance.Create(@"C:\Data\AddToMapCustomItem\AlaskaCitiesXY.csv");
  // Define the tags for the item
  string[] tags = new string[] { "ArcGIS Pro", "SDK", "Internal Demo" };
  // Create the upload definition for the above item
  UploadDefinition uploadDefinition = new UploadDefinition(
    ArcGISPortalManager.Current.GetActivePortal().PortalUri.ToString(),
    itemToUpload,
    tags
    );
  // Upload the item to the Portal
  EsriHttpClient httpClient = new EsriHttpClient();
  var result = httpClient.Upload(uploadDefinition);

  // Manage the result of the operation appropriately
  if (result.Item1 == false)
    return;
}