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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]

DynamoDB - How to implement Optimistic Locking using ServiceStack.Aws

Currently, I am using ServiceStack.Aws v5.9.0 to communicate with DynamoDB. I have used PutItem for both creating and updating an item without anticipating data loss in case of concurrency handling.
public class Customer
{
[HashKey]
public int CustomerId { get; set; }
[AutoIncrement]
public int SubId { get; set; }
public string CustomerType { get; set; }
public string LastName { get; set; }
public string FirstName { get; set; }
...//and hundreds of fields here
}
public class CustomerDynamo
{
private readonly IPocoDynamo db;
//Constructor
public CustomerDynamo()
{
var dynamoClient = new AmazonDynamoDBClient(_region);
var entityType = typeof(Customer);
var tableName = entityType.Name;
entityType.AddAttributes(new AliasAttribute(name: tableName));
db = new PocoDynamo(dynamoClient) { ConsistentRead = true }.RegisterTable(tableType: entityType);
}
public Customer Update(Customer customer)
{
customer.ModifiedDate = DateTime.UtcNow;
db.PutItem(customer);
return customer;
}
}
The above Update method is called in every service/async task that needs to update the data of the customer.
Refer to this article of AWS I decided to implement the Optimistic Locking to save my life from the issue of concurrency requests.
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBContext.VersionSupport.html
Assume that the VersionNumber will be the key for Optimistic Locking. So I added the VersionNumber into the Customer model.
public class Customer
{
[HashKey]
public int CustomerId { get; set; }
[AutoIncrement]
public int SubId { get; set; }
public string CustomerType { get; set; }
public string LastName { get; set; }
public string FirstName { get; set; }
...//and hundreds of fields here
[DynamoDBVersion]
public int? VersionNumber { get; set; }
}
The result is VersionNumber not updated while it should be automatically incremented. I think it is just because the PutItem will override the whole existing item. Is this correct?
I think I need to change from PutItem to UpdateItem in the Update method. The question is how can I generate the expression dynamically to be used with the UpdateItem?
Thanks in advance for any help!
Updates:
Thanks #mythz for the useful information about DynamoDBVersion attribute. Then I tried to remove the DynamoDBVersion and using the UpdateExpression of PocoDynamo as below
public Customer Update(Customer customer)
{
customer.ModifiedDate = DateTime.UtcNow;
var expression = db.UpdateExpression<Customer>(customer.CustomerId).Set(() => customer);
expression.ExpressionAttributeNames = new Dictionary<string, string>()
{
{ "#Version", "VersionNumber" }
};
expression.ExpressionAttributeValues = new Dictionary<string, AttributeValue>()
{
{ ":incr", new AttributeValue { N = "1" } },
{ ":zero", new AttributeValue { N = "0" } }
};
expression.UpdateExpression = "SET #Version = if_not_exists(#Version, :zero) + :incr";
if (customer.VersionNumber.HasValue)
{
expression.Condition(c => c.VersionNumber == customer.VersionNumber);
}
var success = db.UpdateItem(expression);
}
But the changes are not saved except the VersionNumber

The [DynamoDBVersion] is an AWS Object Persistence Model attribute for usage with AWS's DynamoDBContext not for PocoDynamo. i.e. the only [DynamoDB*] attributes PocoDynamo utilizes are [DynamoDBHashKey] and [DynamoDBRangeKey] all other [DynamoDB*] attributes are intended for AWS's Object Persistence Model libraries.
When needed you can access AWS's IAmazonDynamoDB with:
var db = new PocoDynamo(awsDb);
var awsDb = db.DynamoDb;
Here are docs on PocoDynamo's UpdateItem APIs that may be relevant.

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.

Automapper object to object

UPDATE 2:
It seems to be a problem with the containing value in Format.
The Debugger shows me "{{MinValue: 6, MaxValue:44}}" for property Format.
When I change this to .Format = new MyFormat(6,44) it works fine.. so maybe its a problem with the web api 2 I'm using ... but anyway it should just push the source-object to the destination-object ;)
UPDATE:
I removed the originial post and added some real code here. the other classes were only dummies to explain my problem.
By the way: The Problem only occurrs when I add the "Format" Property of type object to the class. otherwise it works fine...
I tried to create an simple example to keep things easy ;) but here are parts of my real code
private void InitAutoMapper()
{
if (_mappingInitialized) //static init
return;
//will prevent Mapper to try to map constructor-parameters. With Copy-Constructors otherwise this would cause infiniteloops and stackoverflowexceptions.
Mapper.Configuration.DisableConstructorMapping();
//From Client to Server
...
Mapper.CreateMap<SDK.Model.Form.Field, Field>();
//From Server to Client
...
Mapper.CreateMap<Field, SDK.Model.Form.Field>();
...
//checks if the configuration was correct.
Mapper.AssertConfigurationIsValid();
_mappingInitialized = true;
}
and this is the call
public string CreateEntityField(SDK.Model.Form.Field field)
{
var mappedField = Mapper.Map<Field>(field);
...
}
my Field-class looks like this (source and destination classes look exactly the same. they are just separated in two different namespaces to have the possibility to add different properties in the future.
public class Field : IEntityRelatedEntity, IModificationTrackObject
{
public string Id { get; set; }
public string Name { get; set; }
public string DisplayName { get; set; }
public string Description { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime ModifiedOn { get; set; }
public int Status { get; set; }
public int SubStatus { get; set; }
...many more fields
public FieldType Type { get; set; }
public object Format { get; set; }
public FieldRequirement Required { get; set; }
public Field()
{
Name = null;
Description = string.Empty;
DisplayName = null;
Type = FieldType.Text;
Required = FieldRequirement.Optional;
CreatedOn = new DateTime();
ModifiedOn = new DateTime();
}
public Field(Field copy)
{
Id = copy.Id;
Format = copy.Format;
...
}
}
and this is the exception I get (sorry parts of this exception are in german but it means that the source and destination-Type of Format are not the same)
exception =
{
Mapping types:\r\nJObject -> JObject
Newtonsoft.Json.Linq.JObject -> Newtonsoft.Json.Linq.JObject
Destination path:
Field.Format.Format
Source value:
{
"MinValue": "2",
"MaxValue": "100"
}
}
The Mapper should just copy the source to the destination for property "Format" and shouldn't care about whats in there...
one more thing: when i Ignore the Format-Property everything works fine, too.
Mapper.CreateMap<SDK.Model.Form.Field, Field>().ForMember(m => m.Format, opt => opt.Ignore());

Reuse index transformer expressions fails on Id

I'm looking to be able to reuse some of the transform expressions from indexes so I can perform identical transformations in my service layer when the document is already available.
For example, whether it's by a query or by transforming an existing document at the service layer, I want to produce a ViewModel object with this shape:
public class ClientBrief
{
public int Id { get; set; }
public string FullName { get; set; }
public string Email { get; set; }
// ellided
}
From this document model:
public class Client
{
public int Id { get; private set; }
public CompleteName Name { get; private set; }
public Dictionary<EmailAddressKey, EmailAddress> Emails { get; private set; }
// ellided
}
public class CompleteName
{
public string Title { get; set; }
public string GivenName { get; set; }
public string MiddleName { get; set; }
public string Initials { get; set; }
public string Surname { get; set; }
public string Suffix { get; set; }
public string FullName { get; set; }
}
public enum EmailAddressKey
{
EmailAddress1,
EmailAddress2,
EmailAddress3
}
public class EmailAddress
{
public string Address { get; set; }
public string Name { get; set; }
public string RoutingType { get; set; }
}
I have an expression to transform a full Client document to a ClientBrief view model:
static Expression<Func<IClientSideDatabase, Client, ClientBrief>> ClientBrief = (db, client) =>
new ClientBrief
{
Id = client.Id,
FullName = client.Name.FullName,
Email = client.Emails.Select(x => x.Value.Address).FirstOrDefault()
// ellided
};
This expression is then manipulated using an expression visitor so it can be used as the TransformResults property of an index (Client_Search) which, once it has been generated at application startup, has the following definition in Raven Studio:
Map:
docs.Clients.Select(client => new {
Query = new object[] {
client.Name.FullName,
client.Emails.SelectMany(x => x.Value.Address.Split(new char[] {
'#'
})) // ellided
}
})
(The Query field is analysed.)
Transform:
results.Select(result => new {
result = result,
client = Database.Load(result.Id.ToString())
}).Select(this0 => new {
Id = this0.client.__document_id,
FullName = this0.client.Name.FullName,
Email = DynamicEnumerable.FirstOrDefault(this0.client.Emails.Select(x => x.Value.Address))
})
However, the transformation expression used to create the index can then also be used in the service layer locally when I already have a Client document:
var brief = ClientBrief.Compile().Invoke(null, client);
It allows me to only have to have one piece of code that understands the mapping from Client to ClientBrief, whether that code is running in the database or the client app. It all seems to work ok, except the query results all have an Id of 0.
How can I get the Id property (integer) properly populated in the query?
I've read a number of similar questions here but none of the suggested answers seem to work. (Changing the Ids to strings from integers is not an option.)

I have a hard time following your sample fully, Really the best way to dig in to this would be with a failing self-contained unit test.
Nonetheless, let's see if I can pull out the important bits.
In the transform, you have two areas where you are working with the id:
...
client = Database.Load(result.Id.ToString())
...
Id = this0.client.__document_id,
...
The result.Id in the first line and the Id = in the second line are expected to be integers.
The Database.Load() expects a string document key and that is also what you see in __document_id.
The confusion comes from Raven's documentation, code, and examples all use the terms id and key interchangeably, but this is only true when you use string identifiers. When you use non-string identifiers, such as ints or guids, the id may be 123, but the document key is still clients/123.
So try changing your transform so it translates:
...
client = Database.Load("clients/" + result.Id)
...
Id = int.Parse(this0.client.__document_id.Split("/")[1]),
...
... or whatever the c# equivalent linq form would be.