Update UITableViewController - ios

Question

I have two ViewControllers (ViewController A, ViewController B). Both are UITableviewController.
In ViewController A, I get the data from a database an put it to List<string>, so I can Display it.
I have a Navigationbar-button to go to ViewController B. In ViewController B I have List with additional Items. I can add the additional item to the database with a swipe action. This works.
When I go back to ViewController A I want to update my List, but I don't know how :(
I tried it with ViewDidAppear, but it does not work.
ViewController A:
public override void ViewDidAppear(bool animated)
{
base.ViewDidAppear(animated);
NavigationItem.Title = "Anwendungsfälle";
// Hier geht es zum Hinzufügen der Anwendungsfeleder / -fälle oder Maßnahmen zum bestehenden Katalog
this.NavigationItem.SetRightBarButtonItem(
new UIBarButtonItem(UIBarButtonSystemItem.Add,
(sender, args) =>
{
var alertController = UIAlertController.Create("Anwendungsfeld hinzufügen", "Wählen Sie eine Option aus", UIAlertControllerStyle.ActionSheet);
// Hier geht es zur Vorgefertigten Bibliothek
alertController.AddAction(UIAlertAction.Create("Aus Bibliothek hinzufügen", UIAlertActionStyle.Default, (Action) =>
{
AddAnFaViewController controller = this.Storyboard.InstantiateViewController("AddAnFaViewController") as AddAnFaViewController;
controller.firmabereich = firmabereich;
controller.bereich = bereich;
controller.zieleid = zieleid;
controller.idafe = idafe;
this.NavigationController.PushViewController(controller, true);
}));
// Abbrechen Knopf
alertController.AddAction(UIAlertAction.Create("Abbrechen", UIAlertActionStyle.Cancel, alert => Console.WriteLine("Cancel clicked")));
PresentViewController(alertController, true, null);
}),
true);
var lines = new List<string>();
using (MySqlConnection connection = new MySqlConnection("Server=xxxx;Port=3306;database=xxxxb;User Id=xxxxx;Password=xxxx;charset=utf8"))
{
string query = $"SELECT DISTINCT Anwendungsfall FROM {firmabereich} WHERE IDAFE LIKE '{idafe}' ORDER BY Anwendungsfall ASC";
string query2 = $"SELECT DISTINCT IDAFA FROM {firmabereich} WHERE IDAFE LIKE '{idafe}' ORDER BY Anwendungsfall ASC";
string query3 = $"SELECT DISTINCT PrioAnFa, Anwendungsfall FROM {firmabereich} WHERE IDAFE LIKE '{idafe}' ORDER BY Anwendungsfall ASC";
MySqlCommand command = new MySqlCommand(query, connection);
MySqlCommand command2 = new MySqlCommand(query2, connection);
MySqlCommand command3 = new MySqlCommand(query3, connection);
connection.Open();
using (MySqlDataReader reader = command.ExecuteReader())
{
while (reader.Read())
{
anwendungsfälle.Add(reader.GetString(0));
}
}
using (MySqlDataReader reader = command2.ExecuteReader())
{
while (reader.Read())
{
anwendungsfälleid.Add(reader.GetString(0));
}
}
using (MySqlDataReader reader = command3.ExecuteReader())
{
while (reader.Read())
{
prio.Add(reader.GetString(0));
}
}
}
TableView.RowHeight = UITableView.AutomaticDimension;
TableView.EstimatedRowHeight = 40f;
TableView.ReloadData();
}

Answer 1

Since reloading data affects the User Interface directly you need to reload data in GCD.
DispatchQueue.main.async {
TableView.ReloadData();
}
GCD is Apple's multi threading concept; so take a time to understand how it works throughout the Application Life Cycle.
This could be the good introduction