EF how to update an object containing a list of objects

Question

I have a class device as follows.

public class Device
{
    public string id { get; set; }
    public string name { get; set; }
    public List<Instructions> Instructions { get; set; }
}

Now I have a view in which there are sections related to the device, and provision for adding Instrunctions to the device.

If the device is new, then it this.context.Devices.Add(device)works fine.

but if I want to edit the device. I find it on Id. It is populated. and if I change an individual property, then it works fine. but I want to update the whole device at once, which does not happen.

My sample code is as follows.

public async Task<bool> AddInstrument(Device device)
{
    try
    {
        var newDevice = this.context.Device
                        .Where(i => i.Id == device.Id).FirstOrDefault();//  i tried find,single or default also

        //adding new device
        if (newDevice == null)
        {
            this.context.Device.Add(device);
            return await this.context.SaveChangesAsync() > 0;
        }

        //if editing the device
        newDevice = device;
        return await this.context.SaveChangesAsync() > 0;
    }
    catch
    {
        throw;
    }
} 

what i want to achieve.

Problem: - I want to update the corresponding device in the database. along with instructions. for example, Previously, a device called "D22" has 3 instructions (a1, a2, a3).

"D22_1", : a1, a3 ( ), a2 (). b1 a4 , a1, a2, b1, b4 D22_1.

: -

, .

1) D22, , , .

device.Name="aaaaa";

this.context.savechanges();

. .

2)

this.context.Entry(device).State = EntityState.Modified;

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Answer 1

:

this.context.Attach(device);
this.context.Entry(device).State = EntityState.Modified;
this.context.SaveChangesAsync();

Answer 2

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