I was trying to fill data base with wep api and while executing method this problem figurated.

Method:

[HttpPost]
[Route("AddNewContactToExistingAccount")]
public async Task<ActionResult<string>> AddNewContactToExistingAccount(string firstName, string secondName, string email)
{
    //Finding contact with same email and adding new contact to account
        var ac = await _dataContext.Accounts.FirstOrDefaultAsync(x => x.Contacts.Any(y => y.Email == email));
        if (ac==null)
        {
            return BadRequest("No account with such email in the system. Create new account with new contact");
        }
        
        var newContact = new Contact();
        newContact.FirstName = firstName;
        newContact.SecondName = secondName;
        newContact.Email = email;
        ac.Contacts.Add(newContact);
        
        _dataContext.Contacts.Add(newContact);
        await _dataContext.SaveChangesAsync();
    
        return Ok("");
   
}

The problem is in ac.Contacts.Add(newContact), but I dont know what is wrong here. Data base strucutre:

public class Account

{

public int Id { get; set; }

public string AccountName { get; set; }

public List<Contact> Contacts { get; set; }

}

  public class Contact
{
    public int Id { get; set; }
    
    public string FirstName { get; set; }
    
    public string SecondName { get; set; }
    
    public string Email { get; set; }
    
    public int AccountId { get; set; }
    
    public Account Account { get; set; }
}

Exception: "System.NullReferenceException: Object reference not set to an instance of an object."

CodePudding user response：

This exception is because you're trying to access a method/property in a null object. Probably you dont instantiate the Contacts list into your Account class.

CodePudding user response：

FIrst question- Do we have foreign key relationships like 1 account can have multiple contacts Second - While saving the contact you are passing only firstname, secondname, email but accountid is missing which is not nullable. that could be the cause of error.