Trying to refer to already existing records in an object and adding it in the database in EF core-CodePudding

Say we have a Car entity that has a one to many relationship with a Driver entity I create records of drivers in the database first, then I try to add them to the car by referring to their Ids registered in the database.

Car {
    // other properties
    public ICollection<Driver> Drivers {get; set;}
}

to achieve this with EF core I used the straightforward following lines of code

   await _context.AddAsync(carInstance) //the carInstance is passed with multiple drivers

If a driver doesn't already exist in the databases it's created,
If a driver already exists, an error of duplicate keys occurs

How can I refer to the already existing records of the drivers without occurrence of that error ?

CodePudding user response：

For the existing records of drivers you need attach them before add them with carInstance

_context.AttachRange(exisitngDrivers);
await _context.AddAsync(carInstance)