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Entity Framework: Unable to add a record

I am new to C# development and I am trying to write something that can insert a record in a DB. I have a simple test, which I hoped would insert a record into the database when I run it.
Model:
namespace Users.Models;
using System.ComponentModel.DataAnnotations.Schema;
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public string EmailAddress { get; set; }
public string HashedPassword { get; set; }
public DateTime Created { get; set; }
}
Test:
namespace Database.Tests;
using Users.Models;
using Xunit;
public class ReferrerTests
{
[Fact]
public void TestInsert()
{
User user = new()
{
Name = "Bob",
EmailAddress = "bob#email.com",
HashedPassword = "hgfj",
};
using MyDbContext ctx = new();
ctx.Users.Add(user);
}
}
Database context:
namespace Database;
using Users.Models;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using Npgsql;
[DbConfigurationType(typeof(Config))]
[SuppressDbSetInitialization]
public class MyDbContext: DbContext
{
public MyDbContext(): base(MakeConnString()) {}
private static string MakeConnString()
{
// Will be moving these to a common location
string OptEnv(string key, string default_) =>
Environment.GetEnvironmentVariable(key) ?? default_;
string Env(string key) =>
Environment.GetEnvironmentVariable(key) ?? throw new MissingFieldException(key);
NpgsqlConnectionStringBuilder builder = new()
{
Host = Env("PGHOST"),
Port = int.Parse(OptEnv("PGPORT", "5432")),
SslMode = Enum.Parse<SslMode>(OptEnv("PGSSLMODE", "Require")),
TrustServerCertificate = true,
Database = OptEnv("PGDATABASE", "postgres"),
Username = OptEnv("PGUSER", "postgres"),
Password = Env("PGPASSWORD")
};
return builder.ConnectionString;
}
public DbSet<User> Users { get; set; }
}
When running this code I get:
System.NullReferenceException: Object reference not set to an instance of an object.
I think I must have something that is preventing the mapping to my database, but I have been unable to figure it out.
EDIT
I think it's probably important I show the DDL of the table as well:
create table public.user
(
id integer generated always as identity primary key,
name text not null
constraint user_name_check
check (length(name) > 0),
email_address text not null unique
constraint user_email_address_check
check (email_address ~* '^.+#.+\..+$'),
-- Ideally use something like
-- https://www.postgresql.org/docs/13/pgcrypto.html
hash_password text not null
constraint user_password_hash_check
check (length(password_hash) > 0),
created timestamp with time zone default CURRENT_TIMESTAMP not null
constraint user_created_check
check (created <= CURRENT_TIMESTAMP)
);
alter table public."user"
owner to postgres;
EDIT 2:
Suggestions to use annotations to try to get the model to map directly to the DDL - still gives the same error, but this is our new model.
namespace Users.Models;
using System.ComponentModel.DataAnnotations.Schema;
[Table("user", Schema="public")]
public class User
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
[Column("id")]
public int Id { get; set; }
[Column("name")]
public string Name { get; set; }
[Column("email_address")]
public string EmailAddress { get; set; }
[Column("hash_password")]
public string HashedPassword { get; set; }
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
[Column("created")]
public DateTime Created { get; set; }
}

I don't know about your DB but your model requires the Id column to have a value (it's not nullable) So you need to proivde a value in order to do that.
If your Id column type is Serial on the DB side, just decorate your Id column with :
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }

Following #DubDub advice, removing the following line fixed it:
[SuppressDbSetInitialization]

Having issues with a dependent property in a referential restraint

I keep getting this error when I try to submit to the database:
A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'NPPRProvId'
Here's where it breaks:
public static bool Save(NPPR_Provider provider, State state, string filename, bool validateBeforeSave = true )
{
using (var db = new NPPRContext(state))
{
var prov = new NPPR_Provider()
{
First = provider.First,
Middle = provider.Middle,
Last = provider.Last,
DateOfBirth = provider.DateOfBirth,
DateOfDeath = provider.DateOfDeath,
Gender = provider.Gender,
SSN = provider.SSN,
DegreeCode = provider.DegreeCode,
BusinessName = provider.BusinessName,
DbaName = provider.DbaName,
Action = "A",
EffectiveDate = "20121212",
EndDate = "99991231",
NPPR_ServLocation = new NPPR_ServLocation()
{
EnrollmentType = provider.NPPR_ServLocation.EnrollmentType,
OrganizationType = provider.NPPR_ServLocation.OrganizationType,
ProviderTypeCode = provider.NPPR_ServLocation.ProviderTypeCode,
IRSTaxAssociations = provider.NPPR_ServLocation.IRSTaxAssociations,
NPIAssociations = provider.NPPR_ServLocation.NPIAssociations,
Address = provider.NPPR_ServLocation.Address
},
NPPR_Header = new NPPR_Header()
{
FileName = filename,
TransactionDate = Utilities.DateTimeToPRNDate(DateTime.Now),
FileLoadDate = DateTime.Now,
SubmitterId = "M00000503",
Purpose = "A",
Action = "A"
}
};
foreach(var npi in prov.NPPR_ServLocation.NPIAssociations)
{
npi.NPIType = prov.NPPR_ServLocation.OrganizationType == "I" ? "1" : "2";
}
prov.NPPR_ServLocation.Licenses = SegmentOrNull<NPPR_Licenses>(provider.NPPR_ServLocation, "Licenses", "LicenseNumber");
prov.NPPR_ServLocation.Certifications = SegmentOrNull<NPPR_Certifications>(provider.NPPR_ServLocation, "Certifications", "CertificationNumber");
prov.NPPR_ServLocation.Specialties = SegmentOrNull<NPPR_Specialties>(provider.NPPR_ServLocation, "Specialties", "SpecialtyCode");
prov.NPPR_ServLocation.Taxonomies = SegmentOrNull<NPPR_Taxonomies>(provider.NPPR_ServLocation, "Taxonomies", "TaxonomyCode");
prov.NPPR_ServLocation.OtherIds = SegmentOrNull<NPPR_OtherIds>(provider.NPPR_ServLocation, "OtherIds", "IdentifierTypeId");
prov.NPPR_ServLocation.GroupAssociations = SegmentOrNull<NPPR_GroupAssociations>(provider.NPPR_ServLocation, "GroupAssociations", "ProviderLocationId");
db.NPPR_Provider.Add(prov);
if (validateBeforeSave)
db.SaveChangesWithValidation();
else
db.SaveChanges();
return true;
}
}
db.SaveChanges() is where, according to the stacktrace, the exception is thrown. This function was originally written for EF Core, but due to issues with the server, I was forced to turn everything to EF6.4. Under Core, this method worked fine, but under EF6, it throws an exception. I've tried a few things I've read on other SO questions but so far no luck.
Specifically the exception throws on the NPPR_Provider primary key, NPPRProvId, which at no point in my code is ever read or written, except to be defined in the model.
In SQL, the NPPRProvId is PK, int, not null
The model involved:
public class NPPR_Provider : Provider
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int NPPRProvId { get; set; }
//[ForeignKey("NPPR_Header")]
public int? NPPRFileId { get; set; }
[ForeignKey("NPPRFileId")]
public NPPR_Header NPPR_Header { get; set; }
[ForeignKey("NPPRProvId")]
public NPPR_ServLocation NPPR_ServLocation { get; set; }
}
What am I doing wrong here and how might I fix it? I'm still fairly new to EF and this is my first major project in EF and MVC, and in the .NET framework in general.

In EF Core the NPPR_ServLocation could be an owned object but to my knowledge in EF 6 there are not owned objects; you need to define them explicitly in a separate table and give them keys.
public class NPPR_Provider : Provider
{
public int NPPR_ProviderId { get; set; }
public NPPR_Header NPPR_Header { get; set; }
public NPPR_ServLocation NPPR_ServLocation { get; set; }
… // data properties here
}
public class NPPR_Header {
public int NPPR_HeaderId {get;set;}
public int NPPR_ProviderId {get;set;}
public NPPR_Provider {get;set;}
… // data properties here
}
public class NPPR_ServLocation {
public int NPPR_ServLocationId {get;set;}
public int NPPR_ProviderId {get;set;}
public NPPR_Provider {get;set;}
… // data properties here.
}

Can't insert entity with foreign key in Entity Framework

I'm building Backend for Mobile Application with ASP.NET MVC Framework.
I have two Objects:
public class CarLogItem : EntityData
{
public CarLogItem(): base()
{
Time = DateTime.Now;
}
public DateTime Time { get; set; }
public int RPM { get; set; }
public int Speed { get; set; }
public int RunTime { get; set; }
public int Distance { get; set; }
public int Throttle { get; set; }
[ForeignKey("Trip")]
public String Trip_id { get; set; }
// Navigation property
public TripItem Trip { get; set; }
}
and
public class TripItem : EntityData
{
public TripItem() : base()
{
UserId = User.GetUserSid();
StartTime = DateTime.Now;
logItems = new List<CarLogItem>();
}
public string UserId { get; set; }
public List<CarLogItem> logItems {get;set;}
public DateTime StartTime { get; set; }
}
and I have controller, which add new CarLogItem to database.
public class CarLogItemController : TableController<CarLogItem>
{
// POST tables/CarLogItem
public async Task<IHttpActionResult> PostCarLogItem(CarLogItem item)
{
var lastItem = db.CarLogItems.OrderByDescending(x => x.Time).FirstOrDefault();
//lastItem = (Query().Where(logitem => true).OrderBy(logitem => logitem.Time)).Last();
//checking if lastItem.Trip isn't null because
// I have entities with Trip field is null, but all of them should have it.
if (lastItem != null && lastItem.Trip != null && item.RunTime > lastItem.RunTime)
{
item.Trip = lastItem.Trip;
}
//In order to test adding of new TripItem entity to database
// I compare item.RunTime with 120, so it always true
else if (lastItem == null || item.RunTime < 120) // < lastItem.RunTime)
{
var newTrip = new TripItem();
item.Trip = newTrip;
}
else
{
throw new ArgumentException();
}
CarLogItem current = await InsertAsync(item);
return CreatedAtRoute("Tables", new { id = current.Id }, current);
}
}
When I'm trying to add new CarLogItem with Trip = null it's ok, but when Trip is particular object it fails with following Exception:
The entity submitted was invalid: Validation error on property 'Id': The Id field is required
How properly to add new CarLogItem with nested TripItem?

I think that you need to populate the Id property on your TripItem, e.g.
var newTrip = new TripItem(){ Id = Guid.NewGuid() }

You need a primary key field in every entity class, like Id or CarLogItemId (ClassName + "Id"). Or just have a property with [Key] attribute:
[Key]
public string/int/Guid/any-db-supported-type MyProp { get; set; }
Entity Framework relies on every entity having a key value that it
uses for tracking entities. One of the conventions that code first
depends on is how it implies which property is the key in each of the
code first classes. That convention is to look for a property named
“Id” or one that combines the class name and “Id”, such as “BlogId”.
The property will map to a primary key column in the database.
Please see this for more details.
I also suspect this to be a problem:
public Lazy<CarLogItem> logItems { get; set; }
You don't have to mark navigation property as Lazy<>. It is already lazy (unless you have configuration that disables lazy loading). Please try to remove Lazy<> and see if it works this way.

Saving primary and foreign keytables at once in EF6

I have primary table and 3 foreign key tables and trying to save all at once. Some time some OK and some time giving error.
public partial class meeting_abstract
{
public int meeting_abstract_id { get; set; }
public int meeting_id { get; set; }
public System.DateTime submission_date { get; set; }
public virtual ICollection<abstract_author> abstract_author { get; set; }
public virtual ICollection<abstract_category> abstract_category { get; set; }
public virtual ICollection<abstract_questions> abstract_questions { get; set; }
}
var meeting_abstract = new meeting_abstract();
meeting_abstract.meeting_id = meetingAbstract.Meeting.meeting_id;
meeting_abstract.submission_date = DateTime.Now;
meeting_abstract.abstract_questions = new Collection<abstract_questions>();
var abstractQuestion = new abstract_questions();
abstractQuestion.meeting_question_id = Convert.ToInt32(meetingAbstract.AbstractTitleInEnglishId);
abstractQuestion.abstract_question_answer = meetingAbstract.AbstractTitleInEnglishText;
meeting_abstract.abstract_questions.Add(abstractQuestion);
abstractQuestion = new abstract_questions();
abstractQuestion.meeting_question_id = Convert.ToInt32(meetingAbstract.AbstractTitleInLanguageId);
abstractQuestion.abstract_question_answer = meetingAbstract.AbstractTitleInLanguageText;
meeting_abstract.abstract_questions.Add(abstractQuestion);
meeting_abstract.abstract_author.Add(meetingAbstract.primaryAuthor);
var abstractCategory = new abstract_category()
{
meeting_category_id = meetingCategory.meeting_category_id
};
meeting_abstract.abstract_category = new Collection<abstract_category>();
meeting_abstract.abstract_category.Add(abstractCategory);
_abstractRewriteEntities.meeting_abstract.Add(meeting_abstract);
_abstractRewriteEntities.SaveChanges();
Whats wrong here? I cannot save all together?

When adding more than one item, with a property defined as the identity, you will need to give those entities a unique key even though it will ultimately be set by the db. We do this in our project by defining a partial class for that entity, and in OnCreated making sure they have a unique value for their identity.
For example:
public partial class abstract_questions
{
private static int _newIdentity = 0;
partial void OnCreated()
{
//Set an identity value so when two new entities
// are created Entity Framework doesn't whinge
// on the server because of duplicate keys
_newIdentity = _newIdentity - 1;
// Set whatever is defined as the identity/pk property
this.Id = _newIdentity;
}

MVC3 EF4 duplicates foreign key object on save

I'm using MVC3 with EF4 code-first. I have the following model:
public class Order {
public int ID { get; set; }
[Required]
public float Price { get; set; }
[Required]
public int PayMethodId { get; set; }
public PayMethod PayMethod { get; set; }
public int? SpecificEventId { get; set; }
public SpecificEvent SpecificEvent { get; set; }
public int? SeasonalTicketId { get; set; }
public SeasonalTicket SeasonalTicket { get; set; }
}
When I try to save an Order object with specificEventId = 2 and specificEvent = X, a new SpecificEvent object is created in the DB, even though there's already a specific event X with ID 2 in the DB. When i try with specificEventId = 2 and specificEvent = null I get a data validation error.
What am I doing wrong? I want SpecificEvent and SeasonalTicket to be nullable, and I don't want EF4 to create a new instance of these objects in the DB whenever I save 'Order'.
Update
This is my code for saving Order in the DB:
public void SaveOrder(Order order)
{
Order fromDb = null;
// If editing an existing object.
if ((fromDb = GetOrder(order.ID)) != null)
{
db = new TicketsDbContext();
db.Entry(order).State = System.Data.EntityState.Modified;
db.SaveChanges();
}
// If adding a new object.
else
{
db.orders.Add(order);
db.SaveChanges();
}
}
When I save, I do reach the else clause.

The real question is, where did you get the instance of X from? It appears as though EF has no knowledge of this instance. You either need to fetch the already existing SpecificEvent through EF and use the proxy it returns to set your navigation property, or else tell EF to "attach" X, so that it knows what your intent is. As far as EF knows, it appears, you are trying to send it a new instance with a conflicting Id, so it is properly issuing the error.