I am writing a simple query to get all the data from a table in a .net core project. When using ToListAsync(), the process crashed without any exceptions thrown. And after changing to ToList(), the process run successfully. I am really curious about the reason behind.
The EF-Core version is 2.2.6.
The same method using TolistAsync(), failed.
public async Task<ICollection<TariffType>> GetAllTariffTypes()
{
using(var dbContext = _dbContextFactory.CreateDbContext(_appConfig.DbContextConnectionString))
{
var tariffTypes = await dbContext.TariffType.ToListAsync();
return tariffTypes;
}
}
The method using ToList(), it worked.
public ICollection<TariffType> GetAllTariffTypes()
{
using(var dbContext = _dbContextFactory.CreateDbContext(_appConfig.DbContextConnectionString))
{
var tariffTypes = dbContext.TariffType.ToList();
return tariffTypes;
}
}
Related
I'm using the in memory database provider for integration tests however I don't seem to be able to update a record. I've run the same code against a real SQL database and everything gets updated fine. Here is my test fixture code.
Test Fixture:
public class TestFixture<TStartup> : IDisposable
{
private readonly TestServer _testServer;
public HttpClient TestClient { get; }
public IDatabaseService DbContext { get { return _testServer.Host.Services.GetService<DatabaseService>(); } }
public TestFixture() : this(Path.Combine("src")) { }
protected TestFixture(string relativeTargetProjectPatentDir)
{
Environment.SetEnvironmentVariable("ASPNETCORE_ENVIRONMENT", "Testing");
var builder = new WebHostBuilder()
.ConfigureServices(services =>
{
services.AddDbContext<DatabaseService>(options =>
options.UseInMemoryDatabase("TestDB")
.EnableSensitiveDataLogging());
})
.UseEnvironment("Testing")
.UseStartup<Startup>();
_testServer = new TestServer(builder)
{
BaseAddress = new Uri("http://localhost:5010")
};
TestClient = _testServer.CreateClient();
TestClient.BaseAddress = _testServer.BaseAddress;
}
public void Dispose()
{
TestClient.Dispose();
_testServer.Dispose();
}
}
I've spent most of the day googling this and not come across any other people talking about it so I'm assuming its probably my issue rather than a EF bug. I'm sure someone would have noticed a DB that you can't update.
Updating works with Singleton but I have CQRS architecture and to check if the entry was updated in e2e test I have to reload entry
Context.Entry(entity).Reload();
I hope that this can help someone
It turned out that changing the lifetime of my DbContext in my test fixture to singleton solved my issue.
Well it can be that DbContext is used in wrong way. I had the same problem. I used the DbContext in same way as you. I simply returned the instance by .Host.Services.GetService<TContext>. The problem with this approach is that DbContext will never release tracked entities so either you set entity State as EntityState.Detached and you force DbContext to reload it, or you will use scopes.
using (var scope = _testServer.Host.Services.GetRequiredService<IServiceScopeFactory>().CreateScope())
{
var dbContext = scope.ServiceProvider.GetRequiredService<DatabaseService>();
//make any operations on dbContext only in scope
}
Adding to Chris's answer. Here is an example of what I had vs. what fixed the issue:
services.AddDbContext<TestDbContext>(options => {
options.UseInMemoryDatabase("TestDb");
});
to
var options = new DbContextOptionsBuilder<TestDbContext>()
.UseInMemoryDatabase(databaseName: "TestDb")
.Options;
services.AddSingleton(x => new TestDbContext(options));
Using AsNoTracking behavior may additionally work below,
services.AddDbContext<TestDbContext>(
a => a.UseInMemoryDatabase(databaseName: "TestDb").UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking),
ServiceLifetime.Singleton)
Also, how are you updating record? This seems to track in EFCore InMemory,
_dbContext.Entry(modifyItem).State = EntityState.Modified;
However, this doesn't seem to work as much.
_dbContext.Entry(existingItem).CurrentValues.SetValues(modifyItem);
I'm a SQL guy who's tinkering with Web API and Entity Framework 6 and I keep receiving the error "The operation cannot be completed because the DbContext has been disposed" when I my code is:
namespace DataAccessLayer.Controllers
{
public class CommonController : ApiController
{
[Route("CorrespondenceTypes")]
[HttpGet]
public IQueryable GetCorrespondenceTypes()
{
using (var coreDB = new coreEntities())
{
var correspondenceType = coreDB.tblCorrespondenceTypes.Select(cor => new { cor.CorrespondenceTypeName });
return correspondenceType;
}
}
}
}
But if change my code around a little and try this it works:
namespace DataAccessLayer.Controllers
{
public class CommonController : ApiController
{
readonly coreEntities coreDB = new coreEntities();
[Route("CorrespondenceTypes")]
[HttpGet]
public IQueryable GetCorrespondenceTypes()
{
var correspondenceType = coreDB.tblCorrespondenceTypes.Select(cor => new { cor.CorrespondenceTypeName });
return correspondenceType;
}
}
}
My question is why does the second one work but not the first? Is it better practice to have a global connection string or call DBContext explicitly each time?
Your are getting error because you are returning the IQueryable for which Entity framework has yet not executed the query and DbContext has been disposed when that query needs to be executed.
Remember Entity framework will not execute query until collection is initialized or any method that does not support deferred execution. Visit this link for list of Linq deferred execution supported method.
why does the second one work but not the first?
In first code snippet you are returning an instance of IQuerable which has not executed DbQuery and then after it just fires dispose on your context (coreDB). So then after whenever your code iterate over the collection it tries to fire DbQuery but finds that context has already been destroyed so you are getting an error.
In second case when ever you are iterating over the collection coreDB context must be alive so you are not getting an error.
Is it better practice to have a global connection string or call DBContext explicitly each time?
Answer to this question is based on developers taste or his own comforts. You can use your context wrapped within using statements as below:
public IList GetCorrespondenceTypes()
{
using (var coreDB = new coreEntities())
{
var correspondenceType = coreDB.tblCorrespondenceTypes.Select(cor => new { cor.CorrespondenceTypeName });
return correspondenceType.ToList();
}
}
As shown in above code snippet if you would use ToList before returning it would execute query before your coreDB got destroyed. In this case you will have to make sure that you returned materialized response (i.e. returned response after executing the DbQuery).
Note: I have noticed most of the people choose the second way. Which targets context as an instance field or property.
In Entity framework, I have implemented generic repository and unit of work pattern.
Below is related stuff from unit of work:
public IRepository<TEntity, TKey> GetRepository<TEntity, TKey>() where TEntity : class
{
if (_repositories == null)
{
_repositories = new Dictionary<string, object>();
}
string key = String.Format("{0}|{1}", typeof(TEntity).Name, typeof(TKey).Name);
if (_repositories.ContainsKey(key))
{
return (IRepository<TEntity, TKey>)_repositories[key];
}
Type repositoryType = typeof(Repository<TEntity, TKey>);
_repositories.Add(key, Activator.CreateInstance(repositoryType, _dataContext));
return (IRepository<TEntity, TKey>)_repositories[key];
}
From Manager layer, entity framework is call as below:
IRepository<tablenameEntity int> _tableEntityRepository = _unitOfWork.GetRepository<tablenameEntity, int>();
Error is as follow:
An error occurred while starting a transaction on the provider connection. See the inner exception for details.
{"New transaction is not allowed because there are other threads running in the session."}.
Actually, I just did as below,
remove stored procedure and function from model browser and added procedure and function again.
run custom tool on edmx file.
It just work out.
I am not sure, what was the issue. did that before also, but it was not work.. now, it works and not produce after that.
Thanks
I have an Asp.Net MVC 4 project using Entity Framework 5.0.
For some reason my DefaultConnectionFactory is not being called when I execute EF code from a Threadpool thread.
I setup my connection factory in the Application_Start event of my Asp.Net MVC project:
Database.DefaultConnectionFactory = new WebConnectionFactory();
This runs successfully on all data access code so far.
I have a Parallel.ForEach loop with a call to some EF code. For some reason the DefaultConnectionFactory is never hit when called. This factory is critical for my code to execute, so the call fails (it uses its default connection string).
Any ideas why this DefaultConnectionFactory would not be called when run on a new thread?
You need to get the connection that you built for each call that you are wanting to use. For example using the following code.
private static void UsingCustomConnection()
{
using (var conn = Database.DefaultConnectionFactory.CreateConnection("YourDbName"))
{
using (var context = new YourContext(conn))
{
context.Destinations.Add(new Destination {Name = "Colorado"});
context.SaveChanges();
}
}
}
You will need to setup this in YourContext
public YourContext(DbConnection connection)
: base(connection, contextOwnsConnection: false)
{
}
I am trying to use mvc-mini-profiler for db-first EF, but it is not working properly.
(note that I'm using objectcontext, not dbcontext)
Here is the list of stackoverflows I've tried:
Setup of mvc-mini-profiler for EF-db- first
How to get MVC-mini-profiler working on EF 4.1 Database First
versions:
Entity Framework: 4.3.1
MiniProfiler: 2.0.2
MiniProfiler.ef: 2.0.3
This is how I setup miniprofiler:
I've added the following stuff in Global.asax
protected void Application_BeginRequest(
{
MiniProfiler.Start();
}
protected void Application_EndRequest()
{
MiniProfiler.Stop();
}
protected void Application_Start()
{
...
MiniProfilerEF.Initialize_EF42();
}
Then configure an objectcontext,
var entityConnection = new EntityConnection(ConnectionString);
var profiledDbConnection = new EFProfiledDbConnection(entityConnection, MiniProfiler.Current);
var context = profiledDbConnection.CreateObjectContext<MyContext>();
var list = context.MyEntities.ToList();
If I execute this, the following exception occurs when running "context.MyEntities.ToList()"
[System.Data.EntityCommandCompliationException]
the message in the inner exception says:
EntityClient cannot be used to create a command definition from a store command tree.
Have I configured wrong? Any help?
thanks,
I use MiniProfiler and database first Entity Framework and it does work well. You may need to turn off the database initialization strategy inside of your database context as per this related answer: https://stackoverflow.com/a/9762989/325727
public class EmployeeContext : DbContext
{
static EmployeeContext() { Database.SetInitializer<EmployeeContext>(null); }
public IDbSet<Employee> Employees { get; set; }
}
The parameter null turns off database initialization by making sure that there is no initializer available.