public BusinessesVM(IDbContextFactory <BusinessDbContext> dbContextFactory, IDbChangeObserver dbChangeObserver)
{
_dbContextFactory = dbContextFactory;
using var dbContext = _dbContextFactory.CreateDbContext();
Businesses = dbContext.Businesses.OrderBy(x => x.Id).ToList();
this.ObserveList <Business>(nameof(Businesses), dbChangeObserver);
}
public ListenOnlyVM(IDbChangeObserver dbChangeObserver)
{
Businesses = new List <Business>();
_subs = dbChangeObserver.Observe <Business>().Subscribe(e =>
{
if (e is DbInsertEvent <Business> )
{
this.AddList(nameof(Businesses), (e as DbInsertEvent <Business>).Row);
}
else if (e is DbUpdateEvent <Business> )
{
this.UpdateList(nameof(Businesses), (e as DbUpdateEvent <Business>).NewRow);
}
else if (e is DbDeleteEvent <Business> )
{
var key = (e as DbDeleteEvent <Business>).Row.Id;
this.RemoveList(nameof(Businesses), key);
}
PushUpdates();
});
}
/// <summary>
/// Observes database changes on the table associated with a view model's list property.
/// </summary>
/// <typeparam name="TTable">Type associated with a database table.</typeparam>
/// <typeparam name="TList">Type associated with the view model's list.</typeparam>
/// <param name="baseVM">View model instance.</param>
/// <param name="listPropName">Property name of the view model's list.</param>
/// <param name="dbChangeObserver">Db change observer service.</param>
/// <param name="selector">Selector to transform TTable instance into TList instance.</param>
public static void ObserveList <TTable, TList>(this BaseVM baseVM, string listPropName, IDbChangeObserver dbChangeObserver, Func <TTable, TList> selector) where TTable : new()
{
listPropName = listPropName ?? throw new ArgumentNullException(nameof(listPropName));
PropertyInfo listProp = baseVM.GetType().GetProperty(listPropName);
listProp = listProp ?? throw new DotNetifyPostgresException($"Property '{baseVM.GetType().Name}.{listPropName}' was not found.");
string itemKeyPropName = listProp.GetCustomAttribute <ItemKeyAttribute>()?.ItemKey;
if (itemKeyPropName == null)
{
itemKeyPropName = baseVM.RuntimeProperties.FirstOrDefault(x => x.Name == $"{listPropName}_itemKey")?.Name;
}
itemKeyPropName = itemKeyPropName ?? throw new DotNetifyPostgresException($"Property '{baseVM.GetType().Name}.{listPropName}' doesn't define an item key.");
PropertyInfo itemKeyPropInfo = typeof(TTable).GetProperty(itemKeyPropName);
bool handleDbChangeEvent(IDbChangeEvent <TTable> dbChangeEvent)
{
if (dbChangeEvent is DbInsertEvent <TTable> )
{
baseVM.AddList(listPropName, selector((dbChangeEvent as DbInsertEvent <TTable>).Row));
}
else if (dbChangeEvent is DbUpdateEvent <TTable> )
{
baseVM.UpdateList(listPropName, selector((dbChangeEvent as DbUpdateEvent <TTable>).NewRow));
}
else if (dbChangeEvent is DbDeleteEvent <TTable> )
{
var key = itemKeyPropInfo.GetValue((dbChangeEvent as DbDeleteEvent <TTable>).Row);
baseVM.RemoveList(listPropName, key);
}
else
{
return(false);
}
baseVM.PushUpdates();
return(true);
}
baseVM.AddInternalProperty <bool>($"{listPropName}_observe").SubscribeTo(dbChangeObserver.Observe <TTable>().Select(handleDbChangeEvent));
}
/// <summary>
/// Observes database changes on the table associated with a view model's list property.
/// </summary>
/// <typeparam name="TTable">Type associated with a database table.</typeparam>
/// <param name="baseVM">View model instance.</param>
/// <param name="listPropName">Property name of the view model's list.</param>
/// <param name="dbChangeObserver">Db change observer service.</param>
public static void ObserveList <TTable>(this BaseVM baseVM, string listPropName, IDbChangeObserver dbChangeObserver) where TTable : new()
{
ObserveList <TTable, TTable>(baseVM, listPropName, dbChangeObserver, _ => _);
}