I try to call a scalar function stored in my DB.
Here is my code:
public class PronosticDbContext : DbContext
{
public PronosticDbContext(DbContextOptions<PronosticDbContext> options) : base(options)
{
}
[DbFunction(FunctionName = "GetPlayerPointsForDay", Schema = "dbo")]
public static int GetPlayerPointsForDay(int dayId, int userId) => throw new NotSupportedException();
}
The call :
private IQueryable<PlayerRankingData> GetPlayerRanking(int? dayId)
{
return Context.Days.Where(x => x.Id == dayId.Value).Select(x => new PlayerRankingData
{
// Some properties
Users = x.Season.Users.Select(us => new PlayerRankingData.User
{
// Other properties
Last = PronosticDbContext.GetPlayerPointsForDay(x.Id, us.User.Id),
// Others again
}).OrderByDescending(u => u.Points).ThenByDescending(u => u.Last).ThenBy(u => u.Login)
});
}
I don't understand why but I always go to the NotSupportedException, my scalar function is never called. Why did I miss ?
I also tried like this, but same result...
modelBuilder
.HasDbFunction(typeof(PronosticDbContext).GetMethod(nameof(GetPlayerPointsForDay)))
.HasSchema("dbo")
.HasName(nameof(GetPlayerPointsForDay));
Ok, I got it.
The thing is you can't call the scalar function directly (I don't know why), it must be encapsulate in a linq query, like this :
Last = Context.Users.Select(u => PronosticDbContext.GetPlayerPointsForDay(x.Id, us.User.Id)).FirstOrDefault()
And that's all. No need to declaration in the DbContext, this is enough :
[DbFunction]
public static int? GetPlayerPointsForDay(int dayId, int userId) => throw new NotSupportedException();
Related
I am trying to use Web API to grab certain fields from my MVC controller. I can't seem to match the right type with the right list. I am fine with converting everything to string.
I either get an error in code (can not convert types), or if I get it to compile, I get this error:
"The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'."
From other similar posts, people responded with how to create a list, but not with the declaration of the return value of the Get. Please include both.
Also I would prefer not to add additional controllers as I need to do this on a number of my models.
Here is my code--note you can see I tried a number of different ways:
public class APICLIENTsController : ApiController
{
private ApplicationDbContext db = new ApplicationDbContext();
// GET api/<controller>
public IEnumerable<string> Get()
//public IEnumerable<CLIENT> Get()
{
//return db.CLIENTs.OrderBy(x => x.CLIENTNAME).ToList();
string[] listOfUsers = db.CLIENTs.OrderBy(x => x.CLIENTNAME).Select(r => new
{
ID = r.CLIENTID.ToString(),
NAME = r.CLIENTNAME
});
return listOfUsers.ToList();
//return db.CLIENTs.Select(x => new { x.CLIENTNAME }).ToArray();
}
If you want to return JSON use the
JsonResult
type.
public JsonResult Get()
{
//return db.CLIENTs.OrderBy(x => x.CLIENTNAME).ToList();
string[] listOfUsers = db.CLIENTs.OrderBy(x => x.CLIENTNAME).Select(r => new
{
ID = r.CLIENTID.ToString(),
NAME = r.CLIENTNAME
});
return Json(listOfUsers.ToList(), JsonRequestBehavior.AllowGet);
}
Your query is returning a collection of anonymous objects, not string[] so it will throw an exception. Even if you were to generate string[] by concatenating the CLIENTID and CLIENTNAME properties, it would be a little use to the client.
Create a model to represent what you need to return to the view
public class ClientVM
{
public int ID { get; set; }
public string Name { get; set; }
}
and modify your method to
public IEnumerable<ClientVM> Get()
{
IEnumerable<ClientVM> model = db.CLIENTs.OrderBy(x => x.CLIENTNAME).Select(r => new ClientVM
{
ID = r.CLIENTID,
Name = r.CLIENTNAME
});
return model;
}
Side note: depending on how your calling and consuming this in the client, you may need to change the Content-Type to specifically return json (refer these answers for more detail)
See the following code:
var source = Peoples.AsQueryable();
IQueryable<People> p;
p = source.Where( x => false);
p = p.Concat(source.Where( x => x.FirstName == "DAVID"));
p = p.Concat(source.Where(x => x.City_id == 3));
p.Dump(); //I use linqpad but it does not matter now
this code work, and linq2sql product one sql-statement (with three qouery and UNION ALL).
now the same code, ostensibly exactly the same procedure, in another variation, throw NotSupportedException:
var q = new IQueryableUnderstand<People>(Peoples.AsQueryable());
q.AddToList(x => x.City_id == 3);
q.AddToList(x => x.FirstName == "Dave");
q.Results().Dump();
IQueryableUnderstand Class:
class IQueryableUnderstand<T>
{
IQueryable<T> _source;
IQueryable<T> combin;
public IQueryableUnderstand(IQueryable<T> source)
{
_source = source;
combin = _source.Where(s => false);
}
public void AddToList(Func<T, bool> predicate) => combin = combin.Concat(_source.Where(predicate));
public IQueryable<T> Results() => combin;
}
LINQ To SQL exception: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains operator
I feel stupid, what's the difference?
Your AddToList() method accepts a Func<T, bool> predicate. The parameter type is incorrect. If applied to your query, it will convert it to a Linq-To-Objects query. IQueryable<TSource> expects expressions, not delegates.
Change your method signature:
public void AddToList(Expression<Func<T, bool>> predicate) =>
combin = combin.Concat(_source.Where(predicate));
I think I'm missing something fundamental when implementing a LinqToHql generator class.
I've successfully registered the SQL Server 2008 contains query using a custom dialect with this registration:
RegisterFunction("contains", new StandardSQLFunction("contains", null));
I have only one class with a full text index to be queried:
public class SearchName
{
public virtual Guid Id {get; set;}
public virtual string Name {get; set;} // this is the search field
}
The contains function works properly in HQL:
var names = Session.CreateQuery("from SearchName where contains(Name,:keywords)")
.SetString("keywords", "john")
.List();
and the generated SQL is perfect:
select searchname0_.Id as Id4_,
searchname0_.Name as Name4_
from Search_Name searchname0_
where contains(searchname0_.Name, 'john' /* #p0 */)
The next challenge was to implement the Linq to HQL generator:
public class MyLinqtoHqlGeneratorsRegistry :
DefaultLinqToHqlGeneratorsRegistry
{
public MyLinqtoHqlGeneratorsRegistry()
{
this.Merge(new ContainsGenerator());
}
}
public class ContainsGenerator : BaseHqlGeneratorForMethod
{
public ContainsGenerator()
{
SupportedMethods = new[] {
ReflectionHelper.GetMethodDefinition<SearchName>(d => d.Name.Contains(String.Empty))
};
}
public override HqlTreeNode BuildHql(MethodInfo method,
System.Linq.Expressions.Expression targetObject,
ReadOnlyCollection<System.Linq.Expressions.Expression> arguments,
HqlTreeBuilder treeBuilder, IHqlExpressionVisitor visitor)
{
return treeBuilder.MethodCall("contains",
visitor.Visit(targetObject).AsExpression(),
visitor.Visit(arguments[0]).AsExpression()
);
}
}
}
Calling the method like this:
var namesLinq = Session.Query<SearchName>().Where(x=> x.Name.Contains("john")).ToList();
Unfortunately, this doesn't seem to override the built-in Contains method, and the generated SQL is wrong:
select searchname0_.Id as Id4_,
searchname0_.Name as Name4_
from Search_Name searchname0_
where searchname0_.Name like ('%' + 'john' /* #p0 */ + '%')
Is it not possible to override the default Contains method, or have I just made a silly mistake?
PS - I'm using NHibernate 3.3.1.4000
OK, I've finally figured it out!
First, I managed to delete the registration code from my configuration:
...
.ExposeConfiguration(cfg =>
{
cfg.LinqToHqlGeneratorsRegistry<MyLinqtoHqlGeneratorsRegistry>();
...
}
Second, don't try to override the existing Linq behaviors. I moved my Contains extension method to the full-text class.
Third, build the Hql tree correctly.
For others trying to implement a SQL 2008 Free-text contains search, here's the complete implementation:
public static class DialectExtensions
{
public static bool Contains(this SearchName sn, string searchString)
{
// this is just a placeholder for the method info.
// It does not otherwise matter.
return false;
}
}
public class MyLinqtoHqlGeneratorsRegistry : DefaultLinqToHqlGeneratorsRegistry
{
public MyLinqtoHqlGeneratorsRegistry()
: base()
{
RegisterGenerator(ReflectionHelper.GetMethod(() =>
DialectExtensions.Contains(null, null)),
new ContainsGenerator());
}
}
public class ContainsGenerator : BaseHqlGeneratorForMethod
{
string fullTextFieldName = "Name";
public ContainsGenerator()
: base()
{
SupportedMethods = new[] {
ReflectionHelper.GetMethodDefinition(() =>
DialectExtensions.Contains(null, null))
};
}
public override HqlTreeNode BuildHql(MethodInfo method,
System.Linq.Expressions.Expression targetObject,
ReadOnlyCollection<System.Linq.Expressions.Expression> arguments,
HqlTreeBuilder treeBuilder, IHqlExpressionVisitor visitor)
{
// cannot figure out how to interrogate the model class to get an
// arbitrary field name...
// perhaps the RegisterGenerator() call above could be used to pass a
// property name to the ContainsGenerator constructor?
// in our case, we only have one full text searchable class, and its
// full-text searchable field is "Name"
HqlExpression[] args = new HqlExpression[2] {
treeBuilder.Ident(fullTextFieldName).AsExpression(),
visitor.Visit(arguments[1]).AsExpression()
};
return treeBuilder.BooleanMethodCall("contains", args);
}
}
For the above to work, you must have declared and used your custom dialect:
public class CustomMsSql2008Dialect : NHibernate.Dialect.MsSql2008Dialect
{
public CustomMsSql2008Dialect()
{
RegisterFunction(
"contains",
new StandardSQLFunction("contains", null)
);
}
}
Then you can use your new contains search this way:
var namesLinq = Session.Query<SearchName>().Where(x => x.Contains("john")).ToList();
... and the resulting SQL is perfect! (at least if you only have one table you're performing full-text searches on)
EDIT: UPDATED IMPLEMENTATION TO SUPPORT MORE THAN ONE FULLTEXT 'Contains' SEARCH PER QUERY.
Here's the revised version:
public static class DialectExtensions
{
public static bool FullTextContains(this string source, string pattern)
{
return false;
}
}
public class MyLinqtoHqlGeneratorsRegistry : DefaultLinqToHqlGeneratorsRegistry
{
public MyLinqtoHqlGeneratorsRegistry()
: base()
{
RegisterGenerator(ReflectionHelper.GetMethod(() => DialectExtensions.FullTextContains(null, null)),
new FullTextContainsGenerator());
}
}
public class FullTextContainsGenerator : BaseHqlGeneratorForMethod
{
public FullTextContainsGenerator()
{
SupportedMethods = new[] { ReflectionHelper.GetMethod(() => DialectExtensions.FullTextContains(null, null)) };
}
public override HqlTreeNode BuildHql(MethodInfo method,
System.Linq.Expressions.Expression targetObject,
ReadOnlyCollection<System.Linq.Expressions.Expression> arguments,
HqlTreeBuilder treeBuilder, IHqlExpressionVisitor visitor)
{
HqlExpression[] args = new HqlExpression[2] {
visitor.Visit(arguments[0]).AsExpression(),
visitor.Visit(arguments[1]).AsExpression()
};
return treeBuilder.BooleanMethodCall("contains", args);
}
}
To use the revised version, the syntax is slightly different:
var namesLinq = Session.Query<SearchName>().Where(x => x.Name.FullTextContains("john")).ToList();
I previously had the following line of code from within my AdminController that was successfully returning a list of relevant subsections from within a course:
[AcceptVerbs(HttpVerbs.Get)]
public JsonResult GetCourseSections(int courseID)
{
var Sections = dbcontext.CourseSection.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new
{
sectionID = x.CourseSectionID,
sectionTitle = x.Title
);
return Json(Sections, JsonRequestBehavior.AllowGet);
}
I was informed to take this out of the controller as it was bad practice to call dbcontext and so i moved this to the AdminViewModel. Within my AdminViewModel I have a variable public List CourseSectionList { get; set; } and I am trying to populate this variable with the JSON request details. My code is as follows:
AdminViewModel
public void GetCourseSectionDetails(int courseID)
{
var Sections = dbcontext.CourseSection.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new CourseSection
{
CourseSectionID = x.CourseSectionID,
Title = x.Title
});
this.CourseSectionList = Sections.ToList();
}
AdminController
[AcceptVerbs(HttpVerbs.Get)]
public JsonResult GetCourseSections(int courseID)
{
avm.GetCourseSectionDetails(courseID);
var Sections = avm.CourseSectionList.Where(cs => cs.CourseID.Equals(courseID)).Select(x => new
{
sectionID = x.CourseSectionID,
sectionTitle = x.Title
});
System.Diagnostics.EventLog.WriteEntry("Application", "JSON=" + Sections.ToList(), System.Diagnostics.EventLogEntryType.Error);
return Json(Sections, JsonRequestBehavior.AllowGet);
}
I am getting the error The entity or complex type 'MetaLearning.Data.CourseSection' cannot be constructed in a LINQ to Entities query. How can I populate this.CourseSectionList variable using the Sections?
As pointed by your error message, you can't, in linq to entities, use a
.Select(m => new <Entity>{bla bla})
where <Entity>... is one of your model's entity.
So either you use a "non model" class (DTO), which has the properties you need, or you have to enumerate before selecting (because linq to objects has not that limitation)
.ToList()
.Select(m => new <Entity>{bla bla});
You can find some nice explanations of why it's not possible here
EDIT :
you may also do something like that, if you wanna retrive only some properties of your entity, and don't wanna use a DTO :
return ctx
.CourseSection
.Where(cs => cs.CourseID.Equals(courseID))
//use an anonymous object to retrieve only the wanted properties
.Select(x => new
{
c= x.CourseSectionID,
t= x.Title,
})
//enumerate, good bye linq2entities
.ToList()
//welcome to linq2objects
.Select(m => new CourseSection {
CourseSectionID = m.c,
Title = m.t,
})
.ToList();
You don't need to repeat the same code in the controller, but directly pass the list to the view.
This being said I am informing you that placing data access code in your view model is even worse practice than keeping it in the controller. I would recommend you having a specific DAL layer:
public interface IRepository
{
public IList<CourseSection> GetSections(int courseID);
}
which would be implemented:
public class RepositoryEF : IRepository
{
public IList<CourseSection> GetSections(int courseID)
{
using (ctx = new YourDbContextHere())
{
return ctx
.CourseSection
.Where(cs => cs.CourseID.Equals(courseID))
.Select(x => new CourseSection
{
CourseSectionID = x.CourseSectionID,
Title = x.Title,
})
.ToList();
}
}
}
and finally have your controller take the repository as dependency:
public class SomeController : Controller
{
private readonly IRepository repo;
public SomeController(IRepository repo)
{
this.repo = repo;
}
[AcceptVerbs(HttpVerbs.Get)]
public ActionResult GetCourseSections(int courseID)
{
var sections = this.repo.GetSections(courseID);
return Json(sections, JsonRequestBehavior.AllowGet);
}
}
I did this as follows using Darin's answer as a guide:
ViewModel
public void GetCourseSectionDetails(int courseID)
{
this.CourseSectionList = dbcontext.CourseSection.AsEnumerable().Where(cs => cs.CourseID.Equals(courseID)).Select(x => new CourseSection
{
CourseSectionID = x.CourseSectionID,
Title = x.Title
}).ToList();
}
Controller
[AcceptVerbs(HttpVerbs.Get)]
public JsonResult GetCourseSections(int courseID)
{
var sections = avm.CourseSectionList;
return Json(sections, JsonRequestBehavior.AllowGet);
}
I have this first version of a class
public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
public IList<Guid> FromDtaObjects(IList<DtaObject> dtaObjects, Employee requestingEmployee)
{
foreach (var dtaObject in dtaObjects) { }
return new List<Guid>();
}
public IList<Guid> FromDtaObjects()
{
return new List<Guid>();
}
}
And the MSpec tests for it
public abstract class specification_for_generate_workflows : Specification<GenerateAuthorisationWorkflows>
{
protected static IWorkflowService workflowService;
Establish context = () => { workflowService = DependencyOf<IWorkflowService>(); };
}
[Subject(typeof(GenerateAuthorisationWorkflows))]
public class when_generate_workflows_is_called_with_a_dta_object_list_and_an_employee : specification_for_generate_workflows
{
static IList<Guid> result;
static IList<DtaObject> dtaObjects;
static Employee requestingEmployee;
Establish context = () =>
{
var mocks = new MockRepository();
var stubDtaObject1 = mocks.Stub<DtaObject>();
var stubDtaObject2 = mocks.Stub<DtaObject>();
var dtaObjectEnum = new List<DtaObject>{stubDtaObject1,stubDtaObject2}.GetEnumerator();
dtaObjects = mocks.Stub<IList<DtaObject>>();
dtaObjects.Stub(x => x.GetEnumerator()).Return(dtaObjectEnum).WhenCalled(x => x.ReturnValue = dtaObjectEnum);
requestingEmployee = mocks.Stub<Employee>();
mocks.ReplayAll();
};
Because of = () => result = subject.FromDtaObjects(dtaObjects, requestingEmployee);
It should_enumerate_the_dta_objects = () => dtaObjects.received(x=> x.GetEnumerator());
It should_call_workflow_host_helper = () => workflowService.AssertWasCalled(x => x.StartWorkflow());
}
With this configuration, my first test passes and my second test fails, as expected. I added a constructor to the class to inject the IWorkflowService.
public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
IWorkflowService _workflowService;
GenerateAuthorisationWorkflows(IWorkflowService workflowService)
{
_workflowService = workflowService;
}
public IList<Guid> FromDtaObjects(IList<DtaObject> dtaObjects, Employee requestingEmployee)
{
foreach (var dtaObject in dtaObjects)
{
Guid workflowKey = _workflowService.StartWorkflow();
}
return new List<Guid>();
}
public IList<Guid> FromDtaObjects()
{
return new List<Guid>();
}
}
Now, when I run the tests, they fail at the Because:
System.InvalidOperationException: Sequence contains no elements
at System.Linq.Enumerable.First(IEnumerable`1 source)
at MSpecTests.EmployeeRequestSystem.Tasks.Workflows.when_generate_workflows_is_called_with_a_dta_object_list_and_an_employee.<.ctor>b__4() in GenerateAuthorisationWorkflowsSpecs.cs: line 76
For clarity, line 76 above is:
Because of = () => result = subject.FromDtaObjects(dtaObjects, requestingEmployee);
I've tried tracing the problem but am having no luck. I have tried setting up a constructor that takes no arguments but it raises the same error. I have similar classes with IoC dependencies that work fine using MSpec/Rhino Mocks, where am I going wrong?
Castle Windsor requires a public constructor to instantiate a class. Adding public to the constructor allows correct operation.
public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
IWorkflowService _workflowService;
public GenerateAuthorisationWorkflows(IWorkflowService workflowService)
{
_workflowService = workflowService;
}
public IList<Guid> FromDtaObjects(IList<DtaObject> dtaObjects, Employee requestingEmployee)
{
foreach (var dtaObject in dtaObjects)
{
Guid workflowKey = _workflowService.StartWorkflow();
}
return new List<Guid>();
}
public IList<Guid> FromDtaObjects()
{
return new List<Guid>();
}
}
Rowan, looks like you answered your own question. It's good practice to explicitly state the access modifiers! By default, C# chooses private. These kinds of errors are easy to miss!
I can also see that your Establish block is too complicated. You're testing the implementation details and not the behavior. For example, you are
stubbing the GetEnumerator call that's implicitly made inside the foreach loop.
asserting that the workflow service was called only once
mixing MSpec automocking and your own local mocks
You're not actually testing that you got a GUID for every object in the input list. If I were you, I'd test the behavior like this...
public class GenerateAuthorisationWorkflows : IGenerateAuthorisationWorkflows
{
private readonly IWorkflowService _service;
public GenerateAuthorisationWorkflows(IWorkflowService service)
{
_service = service;
}
public List<Guid> FromDtaObjects(List<DtaObject> input, Employee requestor)
{
// I assume that the workflow service generates a new key
// per input object. So, let's pretend the call looks like
// this. Also using some LINQ to avoid the foreach or
// building up a local list.
input.Select(x => _service.StartWorkflow(requestor, x)).ToList();
}
}
[Subject(typeof(GenerateAuthorisationWorkflows))]
public class When_generating_authorisation_keys_for_this_input
: Specification<GenerateAuthorisationWorkflows>
{
private static IWorkflowService _service;
private static Employee _requestor = new Employee();
private static List<DtaObject> _input = new List<DtaObject>()
{
new DtaObject(),
new DtaObject(),
};
private static List<Guid> _expected = new List<Guid>()
{
Guid.NewGuid(),
Guid.NewGuid(),
};
private static List<Guid> _actual = new List<Guid>();
Establish context = () =>
{
// LINQ that takes each item from each list in a pair. So
// the service is stubbed to return a specific GUID per
// input DtaObject.
_input.Zip(_expected, (input, output) =>
{
DependencyOf<IWorkflowService>().Stub(x => x.StartWorkflow(_requestor, input)).Return(output);
});
};
Because of = () => _actual = Subject.FromDtaObjects(_input, _requestor);
// This should be an MSpec collection assertion that
// ensures that the contents of the collections are
// equivalent
It should_get_a_unique_key_per_input = _actual.ShouldEqual(_expected);
}