Generic type constraint complation error

[Lars]

I have a compilation error and do not know how to fix it. This is the
first time I've tried to use a generic type constraint.

What have I done wrong?

public sealed class ClassA : IInput
{
...
}

public class ClassB<Twhere T : IInput
{

public ClassB() {...}

public IInput[] Generate()
{
Engine<Tengine = new Engine<T>();
IInput[] lst = engine.ReadFile(someFileName); <===== ERROR:
return lst;
}
}
ERROR: Cannot implicitly convert type 'T[]' to 'IInput[]'

[Hans Kesting]

Lars explained :

I have a compilation error and do not know how to fix it. This is the
first time I've tried to use a generic type constraint.

What have I done wrong?

public sealed class ClassA : IInput
{
...
}

public class ClassB<Twhere T : IInput
{

public ClassB() {...}

public IInput[] Generate()
{
Engine<Tengine = new Engine<T>();
IInput[] lst = engine.ReadFile(someFileName); <===== ERROR:
return lst;
}
}
ERROR: Cannot implicitly convert type 'T[]' to 'IInput[]'

The errormessage says is all:
your 'engine.ReadFile()' method apparently returns a 'T[]' and you are
trying to put that into a 'IInput[]' variable.
Try to use explicit casting (IInput[] lst =
(IInput[])engine.ReadFile(someFileName)), although I don't know whether
that will succeed.
If it fails, store the result in a T[] (maybe you can return that?),
create a new IInput[] of the correct size and copy ann values.

Hans Kesting

[Anthony Jones]

"Hans Kesting" <ne*********@spamgourmet.comwrote in message
news:uj**************@TK2MSFTNGP05.phx.gbl...

Lars explained :

>I have a compilation error and do not know how to fix it. This is the
first time I've tried to use a generic type constraint.

What have I done wrong?

public sealed class ClassA : IInput
{
...
}

public class ClassB<Twhere T : IInput
{

public ClassB() {...}

public IInput[] Generate()
{
Engine<Tengine = new Engine<T>();
IInput[] lst = engine.ReadFile(someFileName); <===== ERROR:
return lst;
}
}
ERROR: Cannot implicitly convert type 'T[]' to 'IInput[]'

The errormessage says is all:
your 'engine.ReadFile()' method apparently returns a 'T[]' and you are
trying to put that into a 'IInput[]' variable.
Try to use explicit casting (IInput[] lst =
(IInput[])engine.ReadFile(someFileName)), although I don't know whether
that will succeed.
If it fails, store the result in a T[] (maybe you can return that?),
create a new IInput[] of the correct size and copy ann values.

The Engine class need to constrain its T to IInput as well for this to work.
That being the case it would probably be best the ReadFile returns IInput[]
instead of T[] anyway.

--
Anthony Jones - MVP ASP/ASP.NET