14、Entity Framework Core 数据操作全解析

Entity Framework Core 数据操作全解析

1. 子对象更改跟踪

在 Entity Framework Core 中，更改跟踪机制同样适用于子对象。以下代码展示了如何加载 Flight 对象及其关联的 Pilot 对象，并对它们进行更改：

public static void ChangeFlightAndPilot()
{
    CUI.MainHeadline(nameof(ChangeFlightAndPilot));
    int flightNo = 101;
    using (WWWingsContext ctx = new WWWingsContext())
    {
        var f = ctx.FlightSet.Include(x => x.Pilot).SingleOrDefault(x => 
x.FlightNo == flightNo);
        Console.WriteLine($"After loading: Flight #{f.FlightNo}:  
{f.Departure}->{f.Destination} has {f.FreeSeats} free seats!\nState  
of the flight object: " + ctx.Entry(f).State + " / State of the  
Pilot object: " + ctx.Entry(f.Pilot).State);
        f.FreeSeats -= 2;
        f.P