Suppose the following:

class MyContainer : System.Collections.CollectionBase
{
//...
}

(where CollectionBase implements IList, ICollection)

How do I determine if a type (such as MyContainer) derives from IList?

System.Type type = typeof(MyContainer);

type is IList -> false

type.IsSubclassOf(typeof(IList)) -> false

type.IsAssignableFrom(typeof(IList)) -> false

etc., all tests return false.

So, what I need is a way to determine if a particular type derives from IList,
no matter how far up the hierarchy it is.

Thanks

Hi!

how about that ? is that too much overkill ?
//***
IList lst = type as IList;
if (lst != null)
Console.WriteLine("type does implement IList");
//***

--
Best Regards
Yanick
"J. Jones" <(E-Mail Removed)> a écrit dans le message de
news:(E-Mail Removed)...
> Suppose the following:
>
> class MyContainer : System.Collections.CollectionBase
> {
> //...
> }
>
> (where CollectionBase implements IList, ICollection)
>
> How do I determine if a type (such as MyContainer) derives from IList?
>
> System.Type type = typeof(MyContainer);
>
> type is IList -> false
>
> type.IsSubclassOf(typeof(IList)) -> false
>
> type.IsAssignableFrom(typeof(IList)) -> false
>
> etc., all tests return false.
>
> So, what I need is a way to determine if a particular type derives from
IList,
> no matter how far up the hierarchy it is.
>
> Thanks

J. Jones wrote:
> How do I determine if a type (such as MyContainer) derives from IList?
Use the C# is statement:
if (MyContainer is IList) {
// Handle IList implementation
}

Anders Norås
http://dotnetjunkies.com/weblog/anoras/

Zoury wrote:
> Hi!
>
> how about that ? is that too much overkill ?

?!

> //***
> IList lst = type as IList;
> if (lst != null)
> Console.WriteLine("type does implement IList");
> //***
>

No go. IList isn't a type, but a class (interface). You can't convert a type
to an instance, what is would happen if permissible in your code.

Anders Norås [MCAD] wrote:
> J. Jones wrote:
>
>> How do I determine if a type (such as MyContainer) derives from IList?
>
> Use the C# is statement:
> if (MyContainer is IList) {
> // Handle IList implementation
> }

No go. I need to test a System.Type variable, so your code becomes something like:

if (typeof(MyContainer) is IList)

which is false.

Thanks

Anders Norås [MCAD] wrote:
> J. Jones wrote:
>
>> How do I determine if a type (such as MyContainer) derives from IList?
>
> Use the C# is statement:
> if (MyContainer is IList) {
> // Handle IList implementation
> }
>
> Anders Norås
> http://dotnetjunkies.com/weblog/anoras/

MyContainer is a class, not a variable, so that won't compile.

This is ugly, but it works:

using System;

interface IWhatever {}

public class App : IWhatever
{
public static void Main()
{
bool implementsIFace =
ImplementsIFace(typeof(ICloneable), typeof(App));
}

static bool ImplementsIFace(Type interfaceType, Type implementingType)
{
Type[] interfaces = implementingType.GetInterfaces();
foreach(Type t in interfaces)
{
if(t == interfaceType) return true;
}
return false;
}
}

/Joakim

oh sorry i did misread your sample.

but i've noticed though that you misread the help file, since the
BaseCollection *does not* implements the Ilist :
---
Public Class BaseCollection
Inherits MarshalByRefObject
Implements ICollection, IEnumerable
---

so here's how you could test it (without any loop) (not tested) :
'***
Console.WriteLine("MyContainer implements IEnumerable : {0}",
typeof(MyContainer).GetInterface("System.Collections.IEnumerable") != null)
'***

--
Best Regards
Yanick

<"Zoury" <yanick_lefebvre at hotmail dot com>> wrote:
> how about that ? is that too much overkill ?
> //***
> IList lst = type as IList;
> if (lst != null)
> Console.WriteLine("type does implement IList");
> //***

It still won't work, for the same reason that "type is IList" won't
work - the Type type itself doesn't implement IList.

--
Jon Skeet - <(E-Mail Removed)>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

"Anders Norås [MCAD]" <(E-Mail Removed)> wrote:
> J. Jones wrote:
> > How do I determine if a type (such as MyContainer) derives from IList?
> Use the C# is statement:
> if (MyContainer is IList) {
> // Handle IList implementation
> }

I believe (given the rest of the post) that the OP is trying to get
that information from the Type reference, not an instance of the type.

--
Jon Skeet - <(E-Mail Removed)>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

J. Jones <(E-Mail Removed)> wrote:
> Suppose the following:
>
> class MyContainer : System.Collections.CollectionBase
> {
> //...
> }
>
> (where CollectionBase implements IList, ICollection)
>
> How do I determine if a type (such as MyContainer) derives from IList?
>
> System.Type type = typeof(MyContainer);
>
> type is IList -> false
>
> type.IsSubclassOf(typeof(IList)) -> false
>
> type.IsAssignableFrom(typeof(IList)) -> false
>
> etc., all tests return false.
>
> So, what I need is a way to determine if a particular type derives from IList,
> no matter how far up the hierarchy it is.

You're using IsAssignableFrom the wrong way round - it's very easy to
do, and I always have to look up the documentation to check it.
Basically, you want

typeof(IList).IsAssignableFrom(type)

--
Jon Skeet - <(E-Mail Removed)>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too