'Specified cast is not valid' when I reload listview items - Xamarin Forms - forms

Question

I'm trying to make an app that saves subjects into an SQLite database and I'm facing an exception: 'Specified cast is not valid'. That happens when I reload the listview items.
(SubjectViewModel.UpdateSubjects())
I receive the data from SubjectServices static class, with async connection.
I set the contentpage binding context to this viewmodel and then set the listview itemssource's binding the SubjectViewModel's SubjectList.
XAML code:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:resx="clr-namespace:MyApp.Resources"
x:Class="MyApp.View.ShellPages.SubjectsPage">
<ContentPage.ToolbarItems>
<ToolbarItem Text="{x:Static resx:AppResources.NewSubject}"
Command="{Binding SubjectNewSCommand}"/>
</ContentPage.ToolbarItems>
<ContentPage.Content>
<ListView x:Name="subjectListView" ItemsSource="{Binding SubjectList}"
IsRefreshing="True" RefreshCommand="{Binding SubjectRefreshCommand}">
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding Name}" Detail="{Binding AddedTime, StringFormat='{0:d}'}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage.Content>
</ContentPage>
SubjectViewModel:
using MyApp.Model;
using MyApp.View.ShellPages;
using MyApp.ViewModel.Commands;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Text;
namespace MyApp.ViewModel
{
public class SubjectViewModel
{
public ObservableCollection<Subject> SubjectList { get; set; }
public SubjectPageRefreshCommand SubjectRefreshCommand { get; set; }
public SubjectNewSubjectCommand SubjectNewSCommand { get; set; }
public SubjectViewModel()
{
SubjectRefreshCommand = new SubjectPageRefreshCommand(this);
SubjectNewSCommand = new SubjectNewSubjectCommand(this);
SubjectList = new ObservableCollection<Subject>();
}
public async void UpdateSubjects()
{
var subjectList = await SubjectServices.GetSubjects();
SubjectList.Clear();
foreach (var subject in subjectList)
SubjectList.Add(subject);
}
public async void Navigate()
{
await App.Current.MainPage.Navigation.PushAsync(new NewSubjectPage());
}
}
}
Subject class:
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using System.Threading.Tasks;
using SQLite;
namespace MyApp.Model
{
public class Subject
{
[PrimaryKey, AutoIncrement]
public int ID { get; set; }
[MaxLength(50)]
public string Name { get; set; }
public DateTime AddedTime { get; set; }
}
}
What could be the problem? I've tried to find any solution but didn't succeed.
I appreciate any kind of help.