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How do I implement a simple "complex type" in Entity Framework Core 2/C#?

I'm using Entity Framework and .Net Core 2.0 for the first time (I'm also pretty new to C#, but I've been using the traditional .Net Framework & VB since version 1... so I'm no newbie to .Net development), and I've already run into a problem creating my database.
Take this simple scenario: I want to store some information about some electric pumps. Two of the properties are a min/max type range, so I've implemented these as a simple class, thus:
public class Pump
{
[Key]
public int pumpId { get; set; }
public string pumpName { get; set; }
public int pumpControlChannel { get; set; }
public MinMax normalCurrent { get; set; }
public MinMax normalFlowRate { get; set; }
}
[ComplexType]
public class MinMax
{
public int min { get; set; }
public int max { get; set; }
}
As you can see, I've tried the [ComplexType] decorator, to no avail.
Anyway, now create a dead simple DBContext class to manage my Pumps class. I'm using Sqlite:
public class EFDB : DbContext
{
public DbSet<Pump> pumps { get; private set; }
private static DbContextOptions GetOptions(string connectionString)
{
var modelBuilder = new DbContextOptionsBuilder();
return modelBuilder.UseSqlite(connectionString).Options;
}
public EFDB(string connectionString) : base(GetOptions(connectionString)) { }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
try
{
// modelBuilder.ComplexType<MinMax>(); // ComplexType not recognised
base.OnModelCreating(modelBuilder);
}
catch (Exception ex)
{
System.Diagnostics.Debugger.Break();
}
}
}
and lastly a simple static class to call it (I embeded it in a bigger program... to duplicate this problem you could just stick the code lines into program.cs):
public static class TryMe
{
public static void MakeMeFail()
{
using (var db = new EFDB("FileName=C:\\temp\\test_effail.db"))
{
try
{
db.Database.EnsureCreated();
}
catch (Exception ex)
{
System.Diagnostics.Debugger.Break(); // If we hit this line, it fell over
}
}
System.Diagnostics.Debugger.Break(); // If we hit this line, it worked.
}
}
Just call TryMe.MakeMeFail(), the code fails at db.Database.EnsureCreated().
From everything I've read, [ComplexType] should do what I want... but it Just Doesn't. Nor can I find modelBuilder.ComplexType<T> anywhere.
It may just be a library reference I'm missing...? The above code uses the following:
using System;
using Microsoft.EntityFrameworkCore;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
However, NONE of the documentation/examples I can find anywhere show which libraries need referencing!
Thanks in advance.
[PS: Apologies to those who already saw this question, I'm using EF Core 2.0, NOT EF6]

Typical... it's always the way, isn't it? 5 minutes after posting, you discover the answer to your own question....
The answer, in this case, can be found here:
https://learn.microsoft.com/en-us/ef/core/modeling/owned-entities
EF Core calls this sort of entity an "owned" entity, rather than a "complex type".
Simply adding these lines to `OnModelCreating' fixed the issue:
modelBuilder.Entity<Pump>().OwnsOne(p => p.normalCurrent);
modelBuilder.Entity<Pump>().OwnsOne(p => p.normalFlowRate);
The database now creates (correctly, I think, I haven't verified that yet).

Dynamically change a type with C#

I am very new to C# and ServiceStack and I am working on a small project that consists on calling a third party API and loading the data I get back from the API into a relational database via ServiceStack's ORMLite.
The idea is to have each endpoint of the API have a reusable model that determines how it should be received in the API's response, and how it should be inserted into the database.
So I have something like the following:
[Route("/api/{ApiEndpoint}", "POST")]
public class ApiRequest : IReturn<ApiResponse>
{
public Int32 OrderId { get; set; }
public DateTime PurchaseDate { get; set; }
public String ApiEndpoint { get; set; }
}
public class ApiResponse
{
public Endpoint1[] Data { get; set; }
public String ErrorCode { get; set; }
public Int32 ErrorNumber { get; set; }
public String ErrorDesc { get; set; }
}
public class Endpoint1
{
[AutoIncrement]
public Int32 Id { get; set; }
[CustomField("DATETIME2(7)")]
public String PurchaseDate { get; set; }
[CustomField("NVARCHAR(50)")]
public String Customer { get; set; }
[CustomField("NVARCHAR(20)")]
public String PhoneNumber { get; set; }
public Int32 Amount { get; set; }
}
My first class represents the API's request with its route, the second class represents the API's response. The API's response is the same for all endpoints, but the only thing that varies is the structure of the Data field that comes back from that endpoint. I've defined the structure of one of my endpoints in my Endpoint1 class, and I am using it in my API's response class. As you can see, I am also defining a few attributes on my Endpoint1 class to help the ORM make better decisions later when inserting the data.
Ok, so the issue is that I have about 15 endpoints and I don't want to create 15 ApiResponse classes when I know the only thing that changes is that first Data field in the class.
So I made something like this:
public class DataModels
{
public Type getModel(String endpoint)
{
Dictionary<String, Type> models = new Dictionary<String, Type>();
models.Add("Endpoint1", typeof(Endpoint1));
// models.Add("Endpoint2", typeof(Endpoint2));
// models.Add("Endpoint3", typeof(Endpoint3));
// and so forth...
return models[endpoint];
}
}
I would like for getModel() to be called when the request is made so that I can pass in the ApiEndpoint field in the ApiRequest class and store the type that I want my Data field to have so that I can dynamically change it in my ApiResponse class.
In addition, there is the ORM part where I iterate over every endpoint and create a different table using the model/type of each endpoint. Something like this:
endpoints.ForEach(
(endpoint) =>
{
db.CreateTableIfNotExists<Endpoint1>();
// inserting data, doing other work etc
}
);
But again, I'd like to be able to call getModel() in here and with that define the model of the specific endpoint I am iterating on.
I've attempted calling getModel() on both places but I always get errors back like cannot use variable as a typeand others... so I am definitely doing something wrong.
Feel free to suggest a different approach to getModel(). This is just what I came up with but I might be ignoring a much simpler approach.

When I DID understand you correctly, you have different API-Calls which all return the same object. The only difference is, that the field "Data" can have different types.
Then you can simply change the type of data to object:
public object Data { get; set; }
And later simply cast this to the required object:
var data1=(Endpoint1[]) response.Data;

You're going to have a very tough time trying to dynamically create .NET types dynamically which requires advanced usage of Reflection.Emit. It's self-defeating trying to dynamically create Request DTOs with ServiceStack since the client and metadata services needs the concrete Types to be able to call the Service with a Typed API.
I can't really follow your example but my initial approach would be whether you can use a single Service (i.e. instead of trying to dynamically create multiple of them). Likewise with OrmLite if the Schema of the POCOs is the same, it sounds like you would be able to flatten your DataModel and use a single database table.
AutoQuery is an example of a feature which dynamically creates Service Implementations from just a concrete Request DTO, which is effectively the minimum Type you need.
So whilst it's highly recommended to have explict DTOs for each Service you can use inheritance to reuse the common properties, e.g:
[Route("/api/{ApiEndpoint}/1", "POST")]
public ApiRequest1 : ApiRequestBase<Endpoint1> {}
[Route("/api/{ApiEndpoint}/2", "POST")]
public ApiRequest2 : ApiRequestBase<Endpoint1> {}
public abstract class ApiRequestBase<T> : IReturn<ApiResponse<T>>
{
public int OrderId { get; set; }
public DateTime PurchaseDate { get; set; }
public string ApiEndpoint { get; set; }
}
And your Services can return the same generic Response DTO:
public class ApiResponse<T>
{
public T[] Data { get; set; }
public String ErrorCode { get; set; }
public Int32 ErrorNumber { get; set; }
public String ErrorDesc { get; set; }
}
I can't really understand the purpose of what you're trying to do so the API design is going to need modifications to suit your use-case.
You're going to have similar issues with OrmLite which is a Typed code-first POCO ORM where you're going to run into friction trying to use dynamic types which don't exist at Runtime where you'll likely have an easier time executing Dynamic SQL since it's far easier to generate a string than a .NET Type.
With that said GenericTableExpressions.cs shows an example of changing the Table Name that OrmLite saves a POCO to at runtime:
const string tableName = "Entity1";
using (var db = OpenDbConnection())
{
db.DropAndCreateTable<GenericEntity>(tableName);
db.Insert(tableName, new GenericEntity { Id = 1, ColumnA = "A" });
var rows = db.Select(tableName, db.From<GenericEntity>()
.Where(x => x.ColumnA == "A"));
Assert.That(rows.Count, Is.EqualTo(1));
db.Update(tableName, new GenericEntity { ColumnA = "B" },
where: q => q.ColumnA == "A");
rows = db.Select(tableName, db.From<GenericEntity>()
.Where(x => x.ColumnA == "B"));
Assert.That(rows.Count, Is.EqualTo(1));
}
Which uses these extension methods:
public static class GenericTableExtensions
{
static object ExecWithAlias<T>(string table, Func<object> fn)
{
var modelDef = typeof(T).GetModelMetadata();
lock (modelDef)
{
var hold = modelDef.Alias;
try
{
modelDef.Alias = table;
return fn();
}
finally
{
modelDef.Alias = hold;
}
}
}
public static void DropAndCreateTable<T>(this IDbConnection db, string table)
{
ExecWithAlias<T>(table, () => {
db.DropAndCreateTable<T>();
return null;
});
}
public static long Insert<T>(this IDbConnection db, string table, T obj, bool selectIdentity = false)
{
return (long)ExecWithAlias<T>(table, () => db.Insert(obj, selectIdentity));
}
public static List<T> Select<T>(this IDbConnection db, string table, SqlExpression<T> expression)
{
return (List<T>)ExecWithAlias<T>(table, () => db.Select(expression));
}
public static int Update<T>(this IDbConnection db, string table, T item, Expression<Func<T, bool>> where)
{
return (int)ExecWithAlias<T>(table, () => db.Update(item, where));
}
}
But it's not an approach I'd take personally, if I absolutely needed (and I'm struggling to think of a valid use-case outside of table-based Multitenancy or sharding) to save the same schema in multiple tables I'd just be using inheritance again, e.g:
public class Table1 : TableBase {}
public class Table2 : TableBase {}
public class Table3 : TableBase {}

ASP.NET Swagger IEnumerable<T>

In Swagger UI I get a model like:
Inline Model [
Inline Model 1
]
Inline Model 1 {
Id (string, optional),
ConnectionString (string, optional),
ConnectionState (string, optional)
}
for a REST Get method like:
public IEnumerable<Device> Get()
{
return new List<Device>();
}
Why is it not displayed correctly?
Adding Swagger Config from comments
public class SwaggerConfig
{
public static void Register()
{
var thisAssembly = typeof(SwaggerConfig).Assembly;
GlobalConfiguration.Configuration .EnableSwagger(c => { c.SingleApiVersion("v1", "api"); }) .EnableSwaggerUi(c => { });
}
}
public class Device
{
public string Id { get; set; }
public string ConnectionString { get; set; }
public string ConnectionState { get; set; }
}

In C# Asp.Net web api, I did this:
1- In SwaggerConfig.cs
.EnableSwagger(c =>
{//add this line
c.SchemaFilter<ApplyModelNameFilter>();
}
2- add a class that implements ISchemaFilter:
class ApplyModelNameFilter : ISchemaFilter
{
public void Apply(Schema schema, SchemaRegistry schemaRegistry, Type type)
{
schema.title = type.Name;
}
}
I got the idea from here

It seems like Swagger and/or NSwag do not handle Generic List/IList/IEnumerable types very well as a base type, perhaps because some frameworks that may try to connect with Swagger don't understand them.
I have worked around this by wrapping my List in another object. So, in your case, you may need to do something like:
public ListResponseObject<T>()
{
public IEnumerable<T> ResponseList {get; set;}
}
And then return from your controller like this:
public ListResponseObject<Device> Get()
{
return new ListResponseObject<Device>{ResponseList = new List<Device>()};
}
Not as simple... but should get it through Swagger better.
We've leveraged this to our advantage. We've applied this technique to all controllers (or something similar) so we have a more standardized response. We can also do this:
public ListResponseObject<T>() : ResponseObject<T>
{
public IEnumerable<T> ResponseList {get; set;}
}
public ResponseObject<T>()
{
public string Message {get; set;}
public string Status {get; set;}
}
And now you have a container that will make downstream handling a little easier.
Not an exact answer, but a work-around that's worked for us. YMMV
UPDATE: Here's a response to a question I posted in the NSwag GitHub issues:
I think its correct as is. Currently swagger and json schema do not support generics (only for arrays) and thus all generic types are expanded to non-generic/specific types... altough the models should be correct but you may end up with lots of classes...
An enhancement for supporting generics is planned but this will be not compliant with swagger and only work with nswag... (No support in swagger ui)

Saving an Item in EF with existing childrens

Im having some problems saving an object (FeatureType) that have a 1-M relationship with Section.
public class FeatureType
{
public int Id { get; set; }
public string Name { get; set; }
[ForeignKey("SectionId")]
public Section Section { get; set; }
public virtual List<ItemType> ItemTypes { set; get; }
}
public class Section
{
public int Id { get; set; }
public string Name { get; set; }
public int Order { get; set; }
public virtual List<FeatureType> Features { get; set; }
}
If The ItemTypes are new i have no problem and the insert is done correctly.
But if i want to add some existing ItemTypes im getting this Error:
An entity object cannot be referenced by multiple instances of
IEntityChangeTracker.
I have been reading about this problem but i havent found a way to solve it, and it might be because of how its designed my application.
Whem im mappinig from my viewModel to my Model, im getting the section ID and getting the section Object from my SectionRepository as this:
private Section GetSection()
{
var section = _sectionRepository.GetSection(SectionId);
return section;
}
And this is what is giving me the problem, as the section is now been tracked by the SectionRepository that have its own context.
How can i solve this? I have tried just creating a new section with the existing ID but it just create me an empty object.
private Section GetSection()
{
var section = new Section{Id=SectionId};
return section;
}
UPDATE
To save my entity i just use :
_repository.Create(featureType.ToModel());
public FeatureType ToModel()
{
var ft = new FeatureType
{
Name = Name,
ControlType = (ControlType)ControlType,
Order = Order,
Required = Required,
RequiredText = RequiredText,
ItemTypes = GetItemTypes().ToList(),
Section = GetSection(),
};
return ft;
}
UPDATE 2: This is how i have my repositories, i wouldn't like to manage any EF in my controller but with some kind of repository or service.
public class EFBaseRepository
{
protected MyContext Db = new MyContext();
public void Dispose(bool disposing)
{
Db.Dispose();
}
}
public class EFFeatureTypeRepository : EFBaseRepository, IFeatureTypeRepository
{
public IQueryable<FeatureType> GetFeatureTypes
{
get { return Db.FeatureTypes.Include("Section").Include("ItemTypes"); }
}
public Message Create(FeatureType feature)
{
try
{
Db.FeatureTypes.Add(feature);
Db.SaveChanges();
return new Message();
}
catch (Exception e)
{
throw;
// return new Message(e, string.Format("Error Creating {0}", feature.GetType()));
}
}
//..Other Methods
}

You say that the SectionRepository has its own context. That is going to cause you problems. The repositories should share a context. The context is a combination of the unit of work and repository patterns. You need to separate the two patterns:
How to migrate towards unit-of-work and repository pattern
EDIT
You can avoid having the DbContext in the Controller by implementing your own Unit Of Work pattern.
public interface IUnitOfWork : IDisposable
{
ISectionRepository SectionRepository {get;}
//etc
int Save();
}
then in your controller:
public ActionResult Create(FeatureTypeCreate featureType)
{
_Uow.SectionRepository.Create(featureType.ToModel());
_Uow.Save(); //Saving is the responsibility of the Unit Of Work
//not the Repository
}
More references:
Implementing the Repository and Unit of Work
Repository and Unit of Work in Entity Framework
John Papa's original source code

Simply, the error you're getting means that the entities were returned from a different instance of your DbContext than from which they are now trying to be saved. Make sure that you're not doing something like using two different usings around your repository and that your repository always makes use of the same DbContext per instantiation.

WebApi with Linq "Extra content at the end of the document" error

I have the following error when I try to query my MVC 4 WebApi service
Extra content at the end of the document
Below is a rendering of the page up to the first error.
55Author Namehttp://images.myserver.com/authorspictures/nophoto.jpg
I looked into the Author class generated by Linq To Sql and found out that the next property of the Author object just after the image URL is this one:
[Association(Name = "Author_Quote", Storage = "_Quotes", ThisKey = "Id", OtherKey = "AuthorId")]
public EntitySet<Quote> Quotes { get; set; }
My undertanding is that there is some problem when generating the XML for this property causing the above error. However I don't know how I can prevent that and make it working correctly. Most examples I found regarding webApi were using POCO lists so they can't help me on this matter.
Any advices?
Below is my code
public class AuthorController : ApiController
{
IAuthorRepository repository;
public AuthorController(IAuthorRepository repository)
{
this.repository = repository;
}
[ResultLimit(20)]
public IQueryable<Author> GetAuthors(){
return repository.GetAuthors();
}
}
public class DBAuthorRepository : IAuthorRepository
{
public IQueryable<Author> GetAuthors()
{
using (var context = new QuotesDataContext())
{
return context.Authors.ToList().AsQueryable();
}
}
}

I found out that it was caused by deffered loading. So I added the following and now it works.
public class DBAuthorRepository : IAuthorRepository
{
public IQueryable<Author> GetAuthors()
{
using (var context = new QuotesDataContext())
{
context.DeferredLoadingEnabled = false; // Added this line
return context.Authors.ToList().AsQueryable();
}
}
}

i'm getting the above error in mvc4 webapi, form #alexandrekow answer, i found the solution:
entity = new BrewedlifeEntities();
entity.ContextOptions.ProxyCreationEnabled = false; // Added this line