public static void Demo_Projection_OneFlight()
{
using (var ctx = new WWWingsContext())
{
CUI.MainHeadline("Projection");
var q = from x in ctx.FlightSet
where x.FlightNo == 101
orderby x.FlightNo
select new Flight()
{
FlightNo = x.FlightNo,
Date = x.Date,
Departure = x.Departure,
Destination = x.Destination,
Seats = x.Seats,
FreeSeats = x.FreeSeats,
};
var f = q.FirstOrDefault();
Console.WriteLine(f + " State: " + ctx.Entry(f).State + " Timestamp: " + ByteArrayToString(f.Timestamp));
ctx.Attach(f);
Console.WriteLine(f + " State: " + ctx.Entry(f).State + " Timestamp: " + ByteArrayToString(f.Timestamp));
f.FreeSeats++;
Console.WriteLine(f + " State: " + ctx.Entry(f).State + " Timestamp: " + ByteArrayToString(f.Timestamp));
var anz = ctx.SaveChanges();
Console.WriteLine("Number of saved changes: " + anz);
}
}
public static void Projection_Change()
{
using (var ctx = new WWWingsContext())
{
CUI.MainHeadline(nameof(Projection_Change));
var q = (from f in ctx.FlightSet
where f.FlightNo > 100
orderby f.FlightNo
select new Flight()
{
FlightNo = f.FlightNo,
Date = f.Date,
Departure = f.Departure,
Destination = f.Destination,
FreeSeats = f.FreeSeats,
Timestamp = f.Timestamp
}).Take(2);
var flightSet = q.ToList();
foreach (var f in flightSet)
{
Console.WriteLine($"Flight Nr {f.FlightNo} from {f.Departure} to {f.Destination} has {f.FreeSeats} free seats!");
}
Console.WriteLine("Number of flights: " + flightSet.Count);
foreach (var f in flightSet)
{
Console.WriteLine("Before attach: " + f + " State: " + ctx.Entry(f).State + " Timestamp: " + ByteArrayToString(f.Timestamp));
ctx.Attach(f);
Console.WriteLine("After attach: " + f + " State: " + ctx.Entry(f).State + " Timestamp: " + ByteArrayToString(f.Timestamp));
f.FreeSeats--;
Console.WriteLine("After Änderung: " + f + " State: " + ctx.Entry(f).State + " Timestamp: " + ByteArrayToString(f.Timestamp));
var anz = ctx.SaveChanges();
Console.WriteLine("Number of saved changes: " + anz);
Console.WriteLine("After saving: " + f + " State: " + ctx.Entry(f).State + " Timestamp: " + ByteArrayToString(f.Timestamp));
}
}
}
public static void RemoveFlightWithKey()
{
Console.WriteLine(nameof(RemoveFlightWithKey));
using (WWWingsContext ctx = new WWWingsContext())
{
// Create a dummy object
var f = new Flight();
f.FlightNo = 123456;
Console.WriteLine($"After creation: Flight #{f.FlightNo}: {f.Departure}->{f.Destination} has {f.FreeSeats} free seats! State of the flight object: " + ctx.Entry(f).State);
// Append dummy object to context
ctx.Attach(f);
Console.WriteLine($"After attach: Flight #{f.FlightNo}: {f.Departure}->{f.Destination} has {f.FreeSeats} free seats! State of the flight object: " + ctx.Entry(f).State);
// Delete flight
ctx.FlightSet.Remove(f);
// or: ctx.Remove(f);
Console.WriteLine($"After remove: Flight #{f.FlightNo}: {f.Departure}->{f.Destination} has {f.FreeSeats} free seats! State of the flight object: " + ctx.Entry(f).State);
try
{
var anz = ctx.SaveChanges();
if (anz == 0)
{
Console.WriteLine("Problem: No changes saved!");
}
else
{
Console.WriteLine("Number of saved changes: " + anz);
}
Console.WriteLine($"After saving: Flight #{f.FlightNo}: {f.Departure}->{f.Destination} has {f.FreeSeats} free seats! State of the flight object: " + ctx.Entry(f).State);
}
catch (Exception ex)
{
Console.WriteLine("Error: " + ex.ToString());
}
}
}
public static void TrackingMode_NoTracking_Attach()
{
CUI.MainHeadline(nameof(TrackingMode_NoTracking_Attach));
CUI.Headline("Attach() before change");
using (WWWingsContext ctx = new WWWingsContext())
{
var flightSet = ctx.FlightSet.AsNoTracking().ToList();
var flight = flightSet[0];
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Detached
ctx.Attach(flight);
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Unchanged
flight.FreeSeats--;
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Modified
int count = ctx.SaveChanges();
Console.WriteLine($"Saved changes: {count}"); // 0
}
CUI.Headline("Attach() after change (change state per property)");
using (WWWingsContext ctx = new WWWingsContext())
{
var flightSet = ctx.FlightSet.AsNoTracking().ToList();
var flight = flightSet[0];
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Detached
flight.FreeSeats--;
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Detached
ctx.Attach(flight);
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Unchanged
// geändertes Attribut bei EFC melden
ctx.Entry(flight).Property(f => f.FreeSeats).IsModified = true;
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Modified
int count = ctx.SaveChanges();
Console.WriteLine($"Saved changes: {count}"); // 1
}
CUI.Headline("Attach() after change (change state per object)");
using (WWWingsContext ctx = new WWWingsContext())
{
ctx.Log();
var flightSet = ctx.FlightSet.AsNoTracking().ToList();
var flight = flightSet[0];
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Detached
flight.FreeSeats--;
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Detached
ctx.Attach(flight);
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Unchanged
ctx.Entry(flight).State = EntityState.Modified;
Console.WriteLine(flight + " object state: " + ctx.Entry(flight).State); // Modified
int count = ctx.SaveChanges();
Console.WriteLine($"Saved changes: {count}"); // 1
}
CUI.Headline("Attach() with non entity class -- not allowed!!!");
using (WWWingsContext ctx = new WWWingsContext())
{
var obj = new FileInfo(@"c:\temp\daten.txt");
try
{
ctx.Attach(obj); // Error: The entity type 'FileInfo' was not found. Ensure that the entity type has been added to the model.
}
catch (Exception e)
{
CUI.PrintError(e);
}
}
}