Entity Framework: How to update child data in foreach loop

Question

see my code

    using (var db = new TestDBContext())
    {
        var existingCustomer = db.Customer
        .Include(a => a.Addresses.Select(x=> x.Contacts))
        .FirstOrDefault(p => p.CustomerID == 5);

        existingCustomer.FirstName = "Test Customer122";

        foreach (var Custaddress in existingCustomer.Addresses.FirstOrDefault(a => a.AddressID == 5))
        {
            //Custaddress.
        }
    }

the foreach raising error

foreach statement cannot operate on variables of type 'EFTest.Addresses' because 'EFTest.Addresses' does not contain a public definition for 'GetEnumerator'

i want to set child entity data in foreach loop and update in such a way as a result parent and child both will be updated. please drive me to right direction to get this job done.

Answer 1

That is because the method .FirstOrDefault returns an object of type source, not a list:

https://msdn.microsoft.com/en-us/library/bb340482(v=vs.110).aspx

Try:

    using (var db = new TestDBContext())
    {
        var existingCustomer = db.Customer
        .Include(a => a.Addresses.Select(x=> x.Contacts))
        .FirstOrDefault(p => p.CustomerID == 5);

        existingCustomer.FirstName = "Test Customer122";

        foreach (var custAddress in existingCustomer.Addresses.Where(a => a.AddressID == 5))
        {
            //do stuff
        }

        db.SaveChanges();
    }