private void InsertButton_Click(object sender, RoutedEventArgs e)
{
int sum = string.IsNullOrEmpty(Sum.Text) ? 0 : int.Parse(Sum.Text);
if (sum > 0)
{
currentUser.AddMoney(sum);
UserInfo.Text = $"User: {currentUser.Id}\nBalance: {currentUser.UserAccount.Balance}";
}
}