Using the ASP.NET WebApi 4 RC, is it possible to have an ApiController's return type be a base class and actually return instances of derived classes? Trying to do this now results in an internal server error (500) when returning xml. Returning json using this method works correctly.
public class Base
{
public int ID { get; set; }
}
public class Derived : Base
{
public string Message { get; set; }
}
public class ValuesController : ApiController
{
public IEnumerable<Base> Get()
{
return new Derived[] {
new Derived(){ Message="test"},
new Derived(){ Message="another"}
};
}
}
It would seem that the XML serialization is what's throwing the error but all I can see is the generic 500 error.
Yes, you need to use the knowntype serialization hint:
[System.Runtime.Serialization.KnownType(typeof(Derived))]
public class Base
{
public int ID { get; set; }
}
You might want to do it programmatically
private static Type[] GetKnownType()
{
var assemblies = AppDomain.CurrentDomain.GetAssemblies();
var knownTypes = new List<Type>();
foreach (var assembly in assemblies)
{
knownTypes.AddRange(assembly.GetTypes().Where(x => x.BaseType == typeof (BaseResponse)).ToArray());
}
return knownTypes.ToArray();
}
Do remember your child class MUST have a default constructor else you will get runtime serialization error.
Related
I'm trying to implement a generic item filter using Entity Framework based on a lambda expression telling me the id field. The following code compiles but of course does not work since EF does not understand the generic function:
public static IQueryable<T> Authorize<T>(this IQueryable<T> items, Func<T, Guid> idGetter) where T : class
{
return items.Where(i => idGetter(i) == new Guid("4A6FE5AF-AB63-4BB3-9D32-88766CF242CC"));
}
var result = context.Items.Authorize(i => i.Id);
How to do this using EF? How to use the expression tree to tell him what field to compare? How to use a generic name in a query that can be handled by Entity Framework?
If your id field is always of type Guid (as your code is suggesting), your classes could implement an interface with a member call Id of type Guid:
public interface MyInterface
{
Guid Id { get; set; }
}
public class Item : MyInterface
{
public Guid Id { get; set; }
// ...
}
Then your Authorize method could look like this:
public static IQueryable<T> Authorize<T>(this IQueryable<T> items) where T : MyInterface
{
return items.Where(i => i.Id == new Guid("4A6FE5AF-AB63-4BB3-9D32-88766CF242CC"));
}
And you can use this as follows:
var result = items.AsQueryable().Authorize();
Based on your comments and using reflection this is my approach:
First, your (simple) Attribute to decorate your "id fields":
[AttributeUsage(AttributeTargets.Property)]
public class IdFieldAttribute : Attribute
{
public IdFieldAttribute()
{
}
}
Then your classes could look like this:
public class Item
{
[IdFieldAttribute]
public Guid YourIdField{ get; set; }
// ...
}
A Reflection helper class for getting your desired field:
public static class ReflectionHelper
{
public static PropertyInfo GetPropertyInfoByAttribute<T>(T o, Type attributeType) where T : class
{
var type = o.GetType();
var propertyInfo = type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
.FirstOrDefault(pi => Attribute.IsDefined(pi, attributeType));
return propertyInfo;
}
}
Once you have this, your Authorize method could look like this:
public static IQueryable<T> Authorize<T>(this IQueryable<T> items) where T : class
{
return items.Where(i => (Guid)ReflectionHelper.GetPropertyInfoByAttribute(i, typeof(IdFieldAttribute)).GetValue(i) == new Guid("4A6FE5AF-AB63-4BB3-9D32-88766CF242CC"));
}
And you can use it as follows:
var result = items.AsQueryable().Authorize();
I don't know if what you're looking for is something like this. Maybe this approach could help you.
Is there a way to inherits from DbSet? I want to add some new properties, like this:
public class PersonSet : DbSet<Person>
{
public int MyProperty { get; set; }
}
But I don't know how to instantiate it in my DbContext
public partial MyContext : DbContext
{
private PersonSet _personSet;
public PersonSet PersonSet
{
get
{
_personSet = Set<Person>(); // Cast Error here
_personSet.MyProperty = 10;
return _personSet;
}
}
}
How can I achieve this?
I have found an answer that works for me. I declare my DbSet properties as my derived interface in my context, e.g.:
IDerivedDbSet<Customer> Customers { get; set; }
IDerivedDbSet<CustomerOrder> CustomerOrders { get; set; }
My implementation includes a private IDbSet which which is assigned in the constructor e.g.:
public class DerivedDbSet<T> : IDerivedDbSet<T> where T : class
{
private readonly IDbSet<T> _dbSet;
public DerivedDbSet(IDbSet<T> dbSet)
{
this._dbSet = dbSet;
}
...
}
My implementation of a derived DbContext interface hides the Set<>() method like so:
new public IDerivedSet<TEntity> Set<TEntity>() where TEntity : class
{
//Instantiate _dbSets if required
if (this._dbSets == null)
{
this._dbSets = new Dictionary<Type, object>();
}
//If already resolved, return stored reference
if (this._dbSets.ContainsKey(typeof (TEntity)))
{
return (IDerivedSet<TEntity>) this._dbSets[typeof (TEntity)];
}
//Otherwise resolve, store reference and return
var resolvedSet = new GlqcSet<TEntity>(base.Set<TEntity>());
this._dbSets.Add(typeof(TEntity), resolvedSet);
return resolvedSet;
}
The derived DbContext returns a newly constructed IDerivedSet or picks it's reference cached in a Dictionary. In the derived DbContext I call a method from the constructor which uses type reflection to go through the DbContexts properties and assigns a value/reference using it's own Set method. See here:
private void AssignDerivedSets()
{
var properties = this.GetType().GetProperties();
var iDerivedSets =
properties.Where(p =>
p.PropertyType.IsInterface &&
p.PropertyType.IsGenericType &&
p.PropertyType.Name.StartsWith("IDerivedSet") &&
p.PropertyType.GetGenericArguments().Count() == 1).ToList();
foreach (var iDerivedSet in iDerivedSets)
{
var entityType = iDerivedSet.PropertyType.GetGenericArguments().FirstOrDefault();
if (entityType != null)
{
var genericSet = this.GetType().GetMethods().FirstOrDefault(m =>
m.IsGenericMethod &&
m.Name.StartsWith("Set") &&
m.GetGenericArguments().Count() == 1);
if (genericSet != null)
{
var setMethod = genericSet.MakeGenericMethod(entityType);
iDerivedSet.SetValue(this, setMethod.Invoke(this, null));
}
}
}
}
Works a treat for me. My context class has navigable set properties of my set type that implements a derived interface inheriting IDbSet. This means I can include query methods on my set type, so that queries are unit testable, instead of using the static extensions from the Queryable class. (The Queryable methods are invoked directly by my own methods).
One solution is to create a class that implements IDbSet and delegates all operations to a real DbSet instance, so you can store state.
public class PersonSet : IDbSet<Person>
{
private readonly DbSet<Person> _dbSet;
public PersonSet(DbSet<Person> dbSet)
{
_dbSet = dbSet;
}
public int MyProperty { get; set; }
#region implementation of IDbSet<Person>
public Person Add(Person entity)
{
return _dbSet.Add(entity);
}
public Person Remove(Person entity)
{
return _dbSet.Remove(entity);
}
/* etc */
#endregion
}
Then in your DbContext, put a getter for your Custom DbSet:
public class MyDbContext: DbContext
{
public DbSet<Person> People { get; set; }
private PersonSet _personSet;
public PersonSet PersonSet
{
get
{
if (_personSet == null)
_personSet = new PersonSet( Set<Person>() );
_personSet.MyProperty = 10;
return _personSet;
}
set
{
_personSet = value;
}
}
}
I solved this using another variable to instantiate the "regular" DbSet.
private DbSet<Person> _persons { get; set; }
public PersonDbSet<Person> Persons { get { return new PersonDbSet(_persons); } }
This way entityframework recognizes the Entity but I can still use my own DbSet class.
I know this is really old and the OP has probably moved on but I was just wondering the same thing myself. EF populates the DbSets inside your MyContext at run time.
I just created MyDbSet<T> that inherits from DbSet<T> and the replaced all references to DbSet<T> with my derived class in MyContext. Running my program failed to instantiate any of the properties.
Next I tried setting the properties to IDbSet<T> since DbSet<T> implements this interface. This DOES work.
Investigating further, the constructors for DbSet are protected and internal (the protected one calls the internal one anyway). So MS have made it pretty hard to roll your own version. You may be able to access the internal constructors through reflection but chances are that EF will not construct your derived class anyway.
I would suggest writing an extension method to plug the functionality into the DbSet object, however you're stuck if you want to store state.
I was wondering if it's possible to use a Templated DTO requested of the type public class
RequestDTO<T, U> where T : class where U : class
{
public T ContextRequest { get; set; }
public U Request { get; set; }
}
And pass it to my service's request...
I've tried a simple example of type
public class MyContext
{
//removed some fields
public int IdUser {get;set;}
}
public class MyType1Request
{
public int IdRequest {get;set;}
}
public class MyType2Request
{
public DateTime SomeReallyImportantDate { get; set; }
}
public class UtenteService : Service
{
public UtenteService()
{
}
public string Any(RequestDTO<MyContext,MyType1Request> request)
{
return string.Format("User:{0} - IDRequest: {1}", request.ContextRequest.IdUser, request.Request.IDRequest);
}
public object Any(RequestDTO<MyContext, MyType2Request> request)
{
return string.Format("Utente:{0} - Data : {1}", request.ContextRequest.IDUtente, request.Request.DataLavorativa);
}
But I got this as far I try to access to the service
Sequence contains more than one matching element
Another solution is to implement in each my DTO Request object a IContext (and maybe IContextExt IContextSpecificManner) into the request object...but I would prefer to use the first approach
Thanks
AFAIK - This should work. The only thing that I am missing here is, you need to register route in apphost like:
Routes.Add>("/Utente/{IdUser}/{IdRequest}")
i have written a generic repository for my base windows which have a problem with.
lets be more specific, there is a little poco class called Unit as following:
public class Unit : BaseEntity
{
public string Name { get; set; }
private ICollection<Good> _goods;
public virtual ICollection<Good> Goods
{
get
{
if(_goods==null)
{
return new List<Good>();
}
return _goods;
}
set { _goods = value; }
}
}
which is inherited from a base entity class as :
public class BaseEntity
{
public int Id { get; set; }
public override string ToString()
{
return Id.ToString();
}
}
and this is my Add section of generic repository class:
public void Add(TEntity entity)
{
if (entity == null) return;
if (Context.Entry(entity).State == EntityState.Detached)
{
Context.Set<TEntity>().Attach(entity);
}
Context.Set<TEntity>().Add(entity);
Context.SaveChanges();
}
before add a new record, max id is fetched from db and placed in IdTextBox and them add method of base form is called which calls aforementioned Add method of base repository. here is the problem, i get this error, "The property 'Id' is part of the object's key information and cannot be modified."
there is also a mapper class that maps every property to its corresponding control which does its job fine.
What is my problem?
Thanks in advance.
i figured out that this problem is occured because of auto detect changes enability which was true.
Getting the following error:
Schema specified is not valid. Errors:
The types in the assembly 'x, Version=1.0.0.0, Culture=neutral,
PublicKeyToken=null' cannot be loaded because the assembly contains
the EdmSchemaAttribute, and the closure of types is being loaded by
name. Loading by both name and attribute is not allowed.
What does this error mean exactly?
I'm trying to shoe-horn into my application an EF model from an existing database.
Before this application was based on CodeFirst and using the repository pattern but for the life of me I can't get this working.
Before I had:
public class BaseModelContext : DbContext
{
public DbSet<User> Users { get; set; }
public DbSet<Role> Roles { get; set; }
}
But in a EF model-first scenario (one where tables already exist in the db), I had to remove these as it didn't seem to like having a repository pattern on DbSet properties.
So I stripped these out, and the repository can then use repository on the classes already defined on the .designer.cs context class (the EF model). This has the EdmSchemaAttribute set inside the generated code.
So how do I get my repository pattern to work in the model-first scenario? What does the above error mean exactly?
EDIT
Added new code:
public class BaseModelContext : DbContext
{
// public DbSet<Location> Locations { get; set; }
public BaseModelContext(string nameOrConnection)
: base(nameOrConnection)
{
}
public BaseModelContext()
{
}
}
public class VisitoriDataContext : BaseModelContext
{
public VisitoriDataContext()
: base("visitoriDataConnection")
{
}
}
public interface IVisitoriDataContextProvider
{
VisitoriDataContext DataContext { get; }
}
public class VisitoriDataContextProvider : IVisitoriDataContextProvider
{
public VisitoriDataContext DataContext { get; private set; }
public VisitoriDataContextProvider()
{
DataContext = new VisitoriDataContext();
}
}
public class VisitoriRepository<T> : IRepository<T> where T : class
{
protected readonly IVisitoriDataContextProvider _ctx;
public VisitoriRepository(IVisitoriDataContextProvider ctx)
{
_ctx = ctx;
}
public T Get(int id)
{
return _ctx.DataContext.Set<T>().Find(id);
}
}
public interface ILocationRepo : IRepository<Location>
{
IEnumerable<Location> GetSuggestedLocationsByPrefix(string searchPrefix);
}
public class LocationRepo : VisitoriRepository<Location>, ILocationRepo
{
public LocationRepo(IVisitoriDataContextProvider ctx)
: base(ctx)
{
}
public IEnumerable<Location> GetSuggestedLocationsByPrefix(string searchPrefix)
{
return Where(l => l.name.Contains(searchPrefix)).ToList();
}
}
The error means that you cannot combine code first mapping (data annotations and fluent API) and EDMX mapping (with EntityObjects!) for entity with the same name. These two approaches are disjunctive.
The rest of your question is not clear.
Btw. building mapping from existing database is called database first not model first.
Decorate the assembly containing the GILayerModel type with [assembly: EdmSchema] attribute.
In my case, I had a class that derived from an entity (code-first class) in another assembly, and I was adding an instance of this class to the DBContext:
in DBEntities project:
public class GISLayer
{
[Key]
[DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
public int GISLayerId { get; set; }
[StringLength(200)]
public string LayerName { get; set; }
public List<GISNode> Nodes { get; set; }
}
in the second assembly:
public class GISLayerModel : DBEntities.GISLayer
{
public new List<GISNodeModel> NodesModel { get; set; }
}
and the cause of error:
[WebMethod]
public void SaveGISLayers(GISLayerModel[] layers)
{
using (DBEntities.DBEntities db = new DBEntities.DBEntities())
{
foreach (var l in layers)
{
if (l.GISLayerId > 0)
{
db.GISLayers.Attach(l); //attaching a derived class
db.Entry(l).State = System.Data.EntityState.Modified;
}
else
db.GISLayers.Add(l); //adding a derived class
SaveGISNodes(l.NodesModel.ToArray(), db);
}
db.SaveChanges();
}
}
So, I used AutoMapper to copy properties of derived class to a new instance of base class:
DBEntities.GISLayer gl = AutoMapper.Mapper.Map<DBEntities.GISLayer>(l);
if (gl.GISLayerId > 0)
{
db.GISLayers.Attach(gl);
db.Entry(gl).State = System.Data.EntityState.Modified;
}
else
db.GISLayers.Add(gl);
That solved the problem.