ObservableCollection issue about xamarin.forms.datagrid HOT 11 CLOSED

 using Autofac;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
using Xamarin.Forms;

namespace XNameSpace
{
    public class TransactionsViewModel:BaseViewModel, INotifyPropertyChanged, IViewModel
    {
        private DatabaseService database;

        private Transaction selectedTransaction;

        private bool isRefreshing;

        public TransactionsViewModel()
        {

            database = new DatabaseService();

            FillTransactions();

            this.Remove = new Command(async () =>
            {
                var answer = await Application.Current.MainPage.DisplayAlert("Attention", "Confirm changes?", "Yes", "No");
                if (selectedTransaction != null)
                {

                    Transactions.Remove(selectedTransaction);
                }
            });

   
        }

        
        public void FillTransactions()
        {
            if (Transactions == null)
            {
                Task.Run(async () =>
                {

                    Transactions = new ObservableCollection<Transaction>(await database.Get<Transaction>());

                    foreach (var _Transaction in Transactions)
                    {
                        await database.Delete(_Transaction);
                    }

                    await AddMockedTransactions();

                    Transactions = new ObservableCollection<Transaction>(await database.Get<Transaction>());
                }
                ).Wait();

            }
        }

        private ObservableCollection<Transaction> Transactions;

        public ObservableCollection<Transaction> Transactions
        {
            get{

                return Transactions;
            }

            set
            {
                Transactions = value;
                OnPropertyChanged();
            }
        }

        private async Task AddMockedTransactions()
        {
            await database.Add(

   

                   new Transaction
                   {

                       transaction_type = "C",

                   }
                   );

            await database.Add(new Transaction
            {


                transaction_type = "R",
            }
                   );

            await database.Add(new Transaction
            {
                //need a decorator  

                transaction_type = "I",
            }
                   );

            await database.Add(new Transaction
            {
                //need a decorator  

                transaction_type = "S",
            }
                   );
        }


        public ICommand Remove { protected set; get; }

        public Transaction SelectedTransaction

        {

            get { return selectedTransaction; }

            set

            {

                selectedTransaction = value;

                System.Diagnostics.Debug.WriteLine("Transaction Type Selected : " + value.transaction_type);

            }

        }
        }
    }
}
`