I've been having an issue with one of my .net core services when using the join statement.
This is the problem code:
public List<Category> GetCategoryList()
{
var catlist = (from m in _mappingProductCategoryRepository.Table
join c in _categoryRepository.Table on m.CategoryId equals c.Id
select c).ToList();
return catlist;
}
and the error it throws is this:
InvalidOperationException: Cannot use multiple context instances within a single query execution. Ensure the query uses a single context instance.
Here is the relevant excerpt from my repository:
public partial class PSRepository<TEntity> : IRepository<TEntity> where TEntity : class
{
private readonly PSContext _db;
public PSRepository(PSContext PSContext)
{
_db = PSContext;
}
public virtual IQueryable<TEntity> Table => _db.Set<TEntity>();
}
And here is my context being registered in the startup.cs file
public void ConfigureContainer(ContainerBuilder builder)
{
builder.RegisterType<PSContext>().As<PSContext>().InstancePerDependency();
builder.RegisterGeneric(typeof(PSRepository<>)).As(typeof(IRepository<>)).InstancePerLifetimeScope();
builder.RegisterType<CategoryService>().As<ICategoryService>().InstancePerLifetimeScope();
}
I've changed the context registration from 'InstancePerDependency' to 'InstancePerLifetimeScope' so that it now looks like this:
builder.RegisterType<PSContext>().As<PSContext>().InstancePerLifetimeScope();
And it seems to have fixed the issue. So being somewhat new to .Net Core my question is whether or not this was the correct fix for the issue? Or have I created further issues for myself further down the line?
I realise I could get rid of the repository and use the context directly but I don't really want to do this.
Any help gratefully received
Related
I've reached a bit of a brick-wall with my current project.
I have three normalised databases, one of which I want to dynamically connect to; these are:
Accounts: For secure account information, spanning clients
Configuration: For managing our clients
Client: Which will be atomic for each of our clients & hold all of their information
I need to use data stored in the "Configuration" database to modify the ConnectionString that will be used to connect to the "Client" database, but this is the bit I'm getting stuck on.
So far I've generated the entities from the databases into a project by hooking up EntityFrameWorkCore Tools and using the "Scaffold-DbContext" command & can do simple look-ups to make sure that the databases are being connected to okay.
Now I'm trying to register the databases by adding them to the ServiceCollection, I have them added in the StartUp class as follows:
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.Configure<MvcOptions>(options =>
{
options.Filters.Add(new RequireHttpsAttribute());
});
services.AddDbContext<Accounts>( options =>
options.UseSqlServer(Configuration.GetConnectionString("Accounts"))
);
services.AddDbContext<Support>(options =>
options.UseSqlServer(Configuration.GetConnectionString("Configuration"))
);
// Erm?
SelectClientDatabase(services);
}
Obviously the next stage is to dip into the "Configuration" database, so I've been trying to keep that contained in "SelectClientDatabase()", which just takes the IServiceCollection as a parameter and is for all intents and purposes empty for now. Over the last few days I've found some excellent write-ups on EFC and I'm currently exploring a CustomConfigurationProvider as a possible route, but I must admit I'm a little lost on starting out in ASP.Net Core.
Is it possible to hook into the freshly added DbContext within the ConfigureServices method? Or can/must I add this database to the service collection at a later point?
Thanks!
Edit 1:
I just found this post, which mentions that a DbContext cannot be used within OnConfiguring as it's still being configured; which makes a lot of sense. I'm now wondering if I can push all three DbContexts into a custom middleware to encapsulate, configure and make the connections available; something new to research.
Edit 2:
I've found another post, describing how to "Inject DbContext when database name is only know when the controller action is called" which looks like a promising starting point; however this is for an older version of ASP.Net Core, according to https://learn.microsoft.com "DbContextFactory" has been renamed so I'm now working to update the example given into a possible solution.
So, I've finally worked it all out. I gave up on the factory idea as I'm not comfortable enough with asp.net-core-2.0 to spend time working it out & I'm rushing head-long into a deadline so the faster options are now the better ones and I can always find time to refactor the code later (lol).
My appsettings.json file currently just contains the following (the relevant bit of appsettings.Developments.json is identical):
{
"ConnectionStrings" : {
"Accounts": "Server=testserver;Database=Accounts;Trusted_Connection=True;",
"Client": "Server=testserver;Database={CLIENT_DB};Trusted_Connection=True;",
"Configuration": "Server=testserver;Database=Configuration;Trusted_Connection=True;"
},
"Logging": {
"IncludeScopes": false,
"Debug": {
"LogLevel": {
"Default": "Warning"
}
},
"Console": {
"LogLevel": {
"Default": "Warning"
}
}
}
}
I've opted to configure the two static databases in the ConfigureServices method of StartUp, these should be configured and ready to use by the time the application gets around to having to do anything. The code there is nice & clean.
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.Configure<MvcOptions>(options =>
{
//options.Filters.Add(new RequireHttpsAttribute());
});
services.AddDbContext<AccountsContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("Accounts"))
);
services.AddDbContext<ConfigContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("Configuration"))
);
services.AddSingleton(
Configuration.GetSection("ConnectionStrings").Get<ConnectionStrings>()
);
}
It turns out that one can be spoilt for choice in how to go about accessing configuration options set in the appsettings.json, I'm currently trying to work out how I've managed to get it to switch to the release version instead of the development one. I can't think what I've done to toggle that...
To get the placeholder config setting I'm using a singleton to hold the string value. This is just dipping into the "ConnectionStrings" group and stuffing that Json into the "ClientConnection" object (detailed below).
services.AddSingleton(
Configuration.GetSection("ConnectionStrings").Get<ClientConnection>()
);
Which populates the following structure (that I've just bunged off in its own file):
[DataContract(Name = "ConnectionStrings")]
public class ClientConnection
{
[DataMember]
public string Client { get; set; }
}
I only want this holding the connection string for the dynamically assigned database, so it's not too jazzy. The "Client" DataMember is what is selecting the correct key in the Json, if I wanted a different named node in the Json I'd rename it to "Accounts", for instance.
Another couple of options I tested, before settling on the Singleton option, are:
services.Configure<ConnectionStrings>(Configuration.GetSection("ConnectionStrings"));
and
var derp = Configuration.GetSection("ConnectionStrings:Client");
Which I discounted, but it's worth knowing other options (they'll probably be useful for loading other configuration options later).
I'm not keen on the way the Controller dependencies work in ASP.Net Core 2, I was hoping I'd be able to hide them in a BaseController so they wouldn't have to be specified in every single Controller I knock out, but I've not found a way to do this yes. The dependencies needed in the Controllers are passed in the constructor, these weirded me out for a while because they're auto-magically injected.
My BaseController is set up as follows:
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.EntityFrameworkCore.Internal;
using ServiceLayer.Entities;
using System;
using System.Collections.Generic;
using System.Linq;
namespace ServiceLayer.Controllers
{
public class BaseController : Controller
{
private readonly ClientConnection connectionStrings;
private readonly AccountsContext accountsContext;
private readonly ConfigurationContext configContext;
public ClientTemplateContext clientContext;
private DbContextServices DbContextServices { get; set; }
public BaseController(AccountsContext accounts, ConfigContext config, ClientConnection connection) : base()
{
accountsContext = accounts;
configContext = config;
connectionStrings = connection;
}
public override void OnActionExecuting(ActionExecutingContext context)
{
base.OnActionExecuting(context);
}
}
}
The code for selecting the database then goes in the "OnActionExecuting()" method; this proved to be a bit of a pain as well, trying to ensure that the dbcontext was set up properly, in the end I settled on:
using System;
using System.Collections.Generic;
using System.Linq;
namespace ServiceLayer.Controllers
{
public class BaseController : Controller
{
private readonly ClientConnection connectionStrings;
private readonly AccountsContext accountsContext;
private readonly ConfigurationContext configContext;
public ClientTemplateContext clientContext;
private DbContextServices DbContextServices { get; set; }
public BaseController(AccountsContext accounts, ConfigurationContext config, ClientConnection connection) : base()
{
accountsContext = accounts;
configContext= config;
connectionStrings = connection;
}
public override void OnActionExecuting(ActionExecutingContext context)
{
// Temporary selection identifier for the company
Guid cack = Guid.Parse("827F79C5-821B-4819-ABB8-819CBD76372F");
var dataSource = (from c in configContext.Clients
where c.Cack == cack
join ds in configContext.DataStorage on c.CompanyId equals ds.CompanyId
select ds.Name).FirstOrDefault();
// Proto-connection string
var cs = connectionStrings.Client;
if (!string.IsNullOrEmpty(cs) && !string.IsNullOrEmpty(dataSource))
{
// Populated ConnectionString
cs = cs.Replace("{CLIENT_DB}", dataSource);
clientContext = new ClientTemplateContext().Initialise(cs);
}
base.OnActionExecuting(context);
}
}
}
new ClientTemplateContext().Initialise() is a bit messy but I'll clean it up when I refactor everything else. "ClientTemplateContext" is the entity-framework-core generated class that ties together all the entities it generated, I've added the following code to that class (I did try putting it in a separate file but couldn't get that working, so it's staying in there for the moment)...
public ClientTemplateContext() {}
private ClientTemplateContext(DbContextOptions options) : base(options) {}
public ClientTemplateContext Initialise(string connectionString)
{
return new ClientTemplateContext().CreateDbContext(new[] { connectionString });
}
public ClientTemplateContext CreateDbContext(string[] args)
{
if (args == null && !args.Any())
{
//Log error.
return null;
}
var optionsBuilder = new DbContextOptionsBuilder<ClientTemplateContext>();
optionsBuilder.UseSqlServer(args[0]);
return new ClientTemplateContext(optionsBuilder.Options);
}
I also included using Microsoft.EntityFrameworkCore.Design; and added the IDesignTimeDbContextFactory<ClientTemplateContext> interface to the class. So it looks like this:
public partial class ClientTemplateContext : DbContext, IDesignTimeDbContextFactory<ClientTemplateContext>
This is where the CreateDbContext(string[] args) comes from & it allows us to create a new instance of a derived context at design-time.
Finally, the code for my test controller is as follows:
using Microsoft.AspNetCore.Mvc;
using ServiceLayer.Entities;
using System.Collections.Generic;
using System.Linq;
namespace ServiceLayer.Controllers
{
[Route("api/[controller]")]
public class ValuesController : BaseController
{
public ValuesController(
AccountsContext accounts,
ConfigurationContext config,
ClientConnection connection
) : base(accounts, config, connection) {}
// GET api/values
[HttpGet]
public IEnumerable<string> Get()
{
var herp = (from c in clientContext.Usage
select c).FirstOrDefault();
return new string[] {
herp.TimeStamp.ToString(),
herp.Request,
herp.Payload
};
}
}
}
This successfully yields data from the database dynamically selected from the DataSource table within the Configuration database!
["01/01/2017 00:00:00","derp","derp"]
If anyone can suggest improvements to my solution I'd love to see them, my solution is mashed together as it stands & I want to refactor it as soon as I feel I'm competent enough to do so.
I am currently using Mehdi El Gueddari's DbContextScope project, I think by the book, and it's awesome. But I came across a problem I'm unsure how to solve today. I have a query that I need to execute using a different database login/user because it requires additional permissions. I can create another connection string in my web.config, but I'm not sure how to specify that for this query, I want to use this new connection string. Here is my usage:
In my logic layer:
private static IDbContextScopeFactory _dbContextFactory = new DbContextScopeFactory();
public static Guid GetFacilityID(string altID)
{
...
using (_dbContextFactory.CreateReadOnly())
{
entity = entities.GetFacilityID(altID)
}
}
That calls into my data layer which would look something like this:
private AmbientDbContextLocator _dbcLocator = new AmbientDbContextLocator();
protected CRMEntities DBContext
{
get
{
var dbContext = _dbcLocator.Get<CRMEntities>();
if (dbContext == null)
throw new InvalidOperationException("No ambient DbContext....");
return dbContext;
}
}
public virtual Guid GetFaciltyID(string altID)
{
return DBContext.Set<Facility>().Where(f => f.altID = altID).Select(f => f.ID).FirstOrDefault();
}
Currently my connection string is set in the default way:
public partial class CRMEntities : DbContext
{
public CRMEntities()
: base("name=CRMEntities")
{}
}
Is it possible for this specific query to use a different connection string and how?
I ended up modifying the source code in a way that feels slightly hacky, but is getting the job done for now. I created a new IAmbientDbContextLocator with a Get<TDbContext> method override that accepts a connection string:
public TDbContext Get<TDbContext>(string nameOrConnectionString) where TDbContext : DbContext
{
var ambientDbContextScope = DbContextScope.GetAmbientScope();
return ambientDbContextScope == null ? null : ambientDbContextScope.DbContexts.Get<TDbContext>(nameOrConnectionString);
}
Then I updated the DbContextCollection to pass this parameter to the DbContext's existing constructor overload. Last, I updated the DbContextCollection maintain a Dictionary<KeyValuePair<Type, string>, DbContext> instead of a Dictionary<Type, DbContext> as its cached _initializedDbContexts where the added string is the nameOrConnectionString param. So in other words, I updated it to cache unique DbContext type/connection string pairs.
Then I can get at the DbContext with the connection I need like this:
var dbContext = new CustomAmbientDbContextLocator().Get<CRMEntities>("name=CRMEntitiesAdmin");
Of course you'd have to be careful your code doesn't end up going through two different contexts/connection strings when it should be going through the same one. In my case I have them separated into two different data access class implementations.
Okay so at work we are developing a system using MVC C# & MongoDB. When first developing we decided it would probably be a good idea to follow the Repository pattern (what a pain in the ass!), here is the code to give an idea of what is currently implemented.
The MongoRepository class:
public class MongoRepository { }
public class MongoRepository<T> : MongoRepository, IRepository<T>
where T : IEntity
{
private MongoClient _client;
private IMongoDatabase _database;
private IMongoCollection<T> _collection;
public string StoreName {
get {
return typeof(T).Name;
}
}
}
public MongoRepository() {
_client = new MongoClient(ConfigurationManager.AppSettings["MongoDatabaseURL"]);
_database = _client.GetDatabase(ConfigurationManager.AppSettings["MongoDatabaseName"]);
/* misc code here */
Init();
}
public void Init() {
_collection = _database.GetCollection<T>(StoreName);
}
public IQueryable<T> SearchFor() {
return _collection.AsQueryable<T>();
}
}
The IRepository interface class:
public interface IRepository { }
public interface IRepository<T> : IRepository
where T : IEntity
{
string StoreNamePrepend { get; set; }
string StoreNameAppend { get; set; }
IQueryable<T> SearchFor();
/* misc code */
}
The repository is then instantiated using Ninject but without that it would look something like this (just to make this a simpler example):
MongoRepository<Client> clientCol = new MongoRepository<Client>();
Here is the code used for the search pages which is used to feed into a controller action which outputs JSON for a table with DataTables to read. Please note that the following uses DynamicLinq so that the linq can be built from string input:
tmpFinalList = clientCol
.SearchFor()
.OrderBy(tmpOrder) // tmpOrder = "ClientDescription DESC"
.Skip(Start) // Start = 99900
.Take(PageLength) // PageLength = 10
.ToList();
Now the problem is that if the collection has a lot of records (99,905 to be exact) everything works fine if the data in a field isn't very large for example our Key field is a 5 character fixed length string and I can Skip and Take fine using this query. However if it is something like ClientDescription can be much longer I can 'Sort' fine and 'Take' fine from the front of the query (i.e. Page 1) however when I page to the end with Skip = 99900 & Take = 10 it gives the following memory error:
An exception of type 'MongoDB.Driver.MongoCommandException' occurred
in MongoDB.Driver.dll but was not handled in user code
Additional information: Command aggregate failed: exception: Sort
exceeded memory limit of 104857600 bytes, but did not opt in to
external sorting. Aborting operation. Pass allowDiskUse:true to opt
in..
Okay so that is easy to understand I guess. I have had a look online and mostly everything that is suggested is to use Aggregation and "allowDiskUse:true" however since I use IQueryable in IRepository I cannot start using IAggregateFluent<> because you would then need to expose MongoDB related classes to IRepository which would go against IoC principals.
Is there any way to force IQueryable to use this or does anyone know of a way for me to access IAggregateFluent without going against IoC principals?
One thing of interest to me is why the sort works for page 1 (Start = 0, Take = 10) but then fails when I search to the end ... surely everything must be sorted for me to be able to get the items in order for Page 1 but shouldn't (Start = 99900, Take = 10) just need the same amount of 'sorting' and MongoDB should just send me the last 5 or so records. Why doesn't this error happen when both sorts are done?
ANSWER
Okay so with the help of #craig-wilson upgrading to the newest version of MongoDB C# drivers and changing the following in MongoRepository will fix the problem:
public IQueryable<T> SearchFor() {
return _collection.AsQueryable<T>(new AggregateOptions { AllowDiskUse = true });
}
I was getting a System.MissingMethodException but this was caused by other copies of the MongoDB drivers needing updated as well.
When creating the IQueryable from an IMongoCollection, you can pass in the AggregateOptions which allow you to set AllowDiskUse.
https://github.com/mongodb/mongo-csharp-driver/blob/master/src/MongoDB.Driver/IMongoCollectionExtensions.cs#L53
I'm trying to share a simple DbContext with 4 DbSets among multiple repositories, each of my repositories inherit from this base class
public class CodeFirstRepository : IDisposable
{
private static MyContext _ctx = new MyContext();
protected MyContext Context
{
get { return _ctx; }
}
public void Dispose()
{
if (Context != null)
{
Context.Dispose();
}
}
}
Question: is this an appropriate way to share a connection between repositories?
I'm getting intermittent failures in my unit tests when accessing the various repositories. An exception is thrown from the repository method GetEntityByName
public IOfferResult GetEntityByName(string name)
{
return Context.Entities.Where(o => o.Name == name).FirstOrDefault()
}
Test method
Tests.Service.TestDelete
threw exception: System.ObjectDisposedException: The ObjectContext
instance has been disposed and can no longer be used for operations
that require a connection.
if the database already exists, the code executes as expected. it also works when i change the implementation of GetEntityByName(string name) to the following non-performant code
public IOfferResult GetEntityByName(string name)
{
foreach (OfferResult offer in Context.Offers)
{
if (offerName.ToLower() == offer.Name.ToLower())
{
return offer;
}
}
}
Question: what is going on here?
bear in mind that if the database exists when i run the tests i don't get the error at all.
tia,
jt
This problem is arising because you are treating the DbContext like a singleton by declaring it as a static field, but then you are treating it like it like a transient instance by disposing it as soon as any instance of CodeFirstRepository gets disposed. For example:
using (var r = new PersonRepository())
{
// do something
} // When you hit the end of this block, your static DbContext is disposed.
using (var r = new IOfferRepository())
{
r.GetEntityByName("test"); // this will fail because the context is still disposed.
}
You should not share contexts this way. If you really want all of your repositories to use a single instance of the DbContext, remove the call to Context.Dispose(). This would fix the problem you're getting right now, but it will likely introduce other problems in the future.
But I would strongly caution against using a single DbContext in a scenario where multiple threads could be trying to access it simultaneously. According to the DbContext specs:
Any instance members are not guaranteed to be thread safe.
You'd be better off just removing the static keyword from your field.
I am using EF4, Microsoft.Entity.CTP, and the latest MOQ. I am trying to create a generic repository class and moq the DBContext using MOQ. Whenever I run my moq test I get "object reference not set to an instance of an object" on this.context.Set().Add(entity); and I don't understand why. The code runs ok without a moq.
public class GenericRepository<TEntity> : IGenericRepository<TEntity> where TEntity : class
{
private IContext context;
public GenericRepository(IContext context)
{
this.context = context;
}
public IList<TEntity> List
{
get { return context.Set<TEntity>().ToList(); }
}
public void Create(TEntity entity)
{
this.context.Set<TEntity>().Add(entity);
this.context.SaveChanges();
}
}
var mock = new Mock<IContext>();
GenericRepository<Product> producRepository = new GenericRepository<Product>(mock.Object);
mock.Setup(x => x.Product.Add(productType));
mock.Setup(x => x.SaveChanges());
productRepository.Create(product);
mock.VerifyAll();
You need to mock out the list implementation behind Set. I'm not at the compute ATM but iirc it's an IDbSet.
Change your code first definitions from DbSet to IDbSet and then you can mock them.
http://blogs.msdn.com/b/efdesign/archive/2010/06/21/productivity-improvements-for-the-entity-framework.aspx
I am considering changing my DbContext.tt file to generate IDbSet instead of DbSet, but only after I get the mocking to work.
I am not saying this makes the rest of the work easy, but it will get you past one problem.
What I need help with is what to do after changing my code first definitions to be based on the EF DbContext interfaces. For example, I create instances of my DbSet objects and add them.
Mock<IPosManContext> posManContext;
posManContext.Object.Set(typeof(note_template));
posManContext.Object.note_template.Add(
new note_template()
{
note_template_id = 1,
act_flag = "Y",
desc_text = "Monday Monday",
last_update_dtm = now,
last_update_user_id = "hsimpson",
});
But I get an error that the DbSet is null.
Microsoft needs to provide a good example of what to do.
They went half the way by providing public interfaces for mocking, but I still need more help.
Joe