"Limitations for the explicit implementation of the interface ..."

Question

I can’t understand why the next job is not working, any ideas? public interface IFieldSimpleItem {}

public interface IFieldNormalItem : IFieldSimpleItem
{ }

public class Person
{
    public virtual T Create<T>()
        where T : IFieldSimpleItem
    {
        return default(T);
    }
}

public class Bose : Person
{
    public override T Create<T>()
        where T : IFieldNormalItem //This is where the error is
    {
        return default(T);
    } 
}

The reason I do this is because if a developer inherits from Bose, Bose relies on the instantiated instance, being at least from IFieldNormalItem. Whereas the following only relies on the fact that it is an IFieldSimpleItem, but the above should make it at least IFieldNormalItem.

public class Person
{
    public virtual IFieldSimpleItem Create() 
    {
        return null;
    }
}

public class Bose : Person
{
    public override IFieldSimpleItem Create()  
    {
        return null;
    } 
}

Cheers Anthony

Answer 1

, . , , .

, , .

, Non-Virtual, CheckCreatedType, - , Create.

public class A
{
    public IFieldSimpleItem Create()
    {
        IFieldSimpleItem created = InternalCreate();
        CheckCreatedType(created);
        return created;
    }

    protected virtual IFieldSimpleItem InternalCreate()
    {
        return new SimpleImpl();
    }
    protected virtual void CheckCreatedType(IFieldSimpleItem item)
    { 
        // base class doesn't care. compiler guarantees IFieldSimpleItem
    }
}
public class B : A
{
    protected override IFieldSimpleItem InternalCreate()
    {
        // does not call base class.
        return new NormalImpl();
    }
    protected override void CheckCreatedType(IFieldSimpleItem item)
    {
        base.CheckCreatedType(item);
        if (!(item is IFieldNormalItem))
            throw new Exception("I need a normal item.");

    }
}

. , . , base.CheckCreatedType(item).

() .

2: () .

public class A
{
    public IFieldSimpleItem Create()
    {
        IFieldSimpleItem created = InternalCreate();
        CheckCreatedType(created);
        return created;
    }

    protected virtual IFieldSimpleItem InternalCreate()
    {
        return new SimpleImpl();
    }

    private void CheckCreatedType(IFieldSimpleItem item)
    {
        Type inspect = this.GetType();
        bool keepgoing = true;
        while (keepgoing)
        {
            string name = inspect.FullName;
            if (CheckDelegateMethods.ContainsKey(name))
            {
                var checkDelegate = CheckDelegateMethods[name];
                if (!checkDelegate(item))
                    throw new Exception("failed check");
            }
            if (inspect == typeof(A))
            {
                keepgoing = false;
            }
            else
            {
                inspect = inspect.BaseType;
            }
        }
    }

    private static Dictionary<string,Func<IFieldSimpleItem,bool>> CheckDelegateMethods = new Dictionary<string,Func<IFieldSimpleItem,bool>>();
    protected static void RegisterCheckOnType(string name, Func<IFieldSimpleItem,bool> checkMethod )
    {
        CheckDelegateMethods.Add(name, checkMethod);
    }
}
public class B : A
{
    static B()
    {
        RegisterCheckOnType(typeof(B).FullName, o => o is IFieldNormalItem);
    }

    protected override IFieldSimpleItem InternalCreate()
    {
        // does not call base class.
        return new NormalImpl();
    }
}

, , , . , - , .

, , . , System.Diagnostics.Conditional("DEBUG")], Release .

, , , . : . , Register.., ,

* , , , , ; , .

Answer 2

, .

, :

public interface IFieldSuperItem : IFieldSimpleItem

Person p = new Boss();
p.Create<IFieldSuperItem>();

, Create in Person, , Boss ( IFieldNormalItem ).

Answer 3

, , . , . - , .

public class Bose : Person
{
    public virtual T CreateNormal<T>()
        where T : IFieldNormalItem //This is where the error is
    {
        return default(T);
    } 
}

Person .

Answer 4

, , Create?

public class Person<T> where T : IFieldSimpleItem
{
    public virtual T Create()
    {
        return default(T);
    }
}

public class Bose<T> : Person<T> where T : IFieldNormalItem
{
    public override T Create()
    {
        return default(T);
    } 
}

Answer 5

, , .

, Create :

public interface IFieldSimpleItem { }

public interface IFieldNormalItem : IFieldSimpleItem{ }

public interface IFieldCreator<TField, TPerson> where TField : IFieldSimpleItem where TPerson : Person
{
    TField Create(TPerson person);
}

public class Person
{
}

public class Bose : Person
{
}

public class PersonFieldCreator : IFieldCreator<IFieldSimpleItem, Person> 
{
    public IFieldSimpleItem Create(Person person) { return null; }
}

public class BoseFieldCreator : IFieldCreator<IFieldNormalItem, Bose>
{
    public IFieldNormalItem Create(Bose person) { return null; }
}

Answer 6

:

public interface IFieldNormalItem : IFieldSimpleItem
{ }

public class Person<T> where T : IFieldSimpleItem
{
    public virtual T Create()
    {
        return default(T);
    }
}

Person<IFieldSimpleItem> ( Person) Person<IFieldNormalItem> ( Bose).

Answer 7

, . T IFieldSimpleItem Person.

public class Bose : Person
{
    public override T Create<T>()
        // where T : IFieldNormalItem // You don't need this line.
    {
        return default(T);
    } 
}

: , . , ; Create "override", "virtual".

public class Bose : Person
{
    public virtual T Create<T>()
        where T : IFieldNormalItem
    {
        return default(T);
    } 
}

Answer 8

- . Person, Bose, , Bose.

Person[] people;
[...initialize this somewhere...]

foreach(Person p in people)
  p.Create<IFieldSimpleItem>();