Given the following code....
// FooBar.cs, builds Activate.dll
using System;
public interface IFoo
{
void Bar();
}
public class FooBar : IFoo
{
public FooBar()
{
}
public void Bar()
{
Console.WriteLi ne( "FooBar" );
}
}
// End of FooBar.cs
// DoActivate.cs, builds DoActivate.exe
using System;
using System.Reflecti on;
class Class1
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main(string[] args)
{
IFoo ifoo;
Object obj;
try
{
Assembly a = Assembly.LoadFr om( "Activate.d ll" );
Type[] ts = a.GetTypes();
foreach( Type t in ts )
{
if( t.Name == "FooBar" )
{
if( t.GetInterface( "IFoo" ) != null )
{
obj = Activator.Creat eInstance( t );
ifoo = obj as IFoo;
if( ifoo == null )
Console.WriteLi ne("didn't get object" );
else
Console.WriteLi ne("got object" );
}
else
Console.WriteLi ne( "Object does not support
IFoo" );
}
}
}
catch( Exception e )
{
Console.WriteLi ne( "Caught exception {0}", e );
}
}
}
// End of DoActivate.cs
Why is ifoo null? I always get "didn't get object" and yet everything
appears correct, at least to my untrained eye. Thanks in advance!
3  10883 
Mattias Sjögren wrote: Andy,
Why are you using Assembly.LoadFr om on an assembly that you obviously
have referenced at design time?
Ultimately I want to be able to dynamically load other implementations
of IFoo. This is just a trivial example to display the problem I am
having, not with LoadFrom (it seems to work fine), but with attempting
to treat the returned object as an IFoo. Everything seems to say I
should be able to do this (i.e. code samples, the fact that GetInterface
says it's available, ...), yet when I actually try to cast the object
to an IFoo, it fails.
Interestingly enough, if I create the object via new, I am able to cast
it without a problem.
Why is ifoo null?
http://www.gotdotnet.com/team/clr/Lo...Isolation.aspx
http://blogs.gotdotnet.com/suzcook/P...7-0a144c8dbf16
Mattias
Andy, Ultimately I want to be able to dynamically load other implementations
of IFoo.
In that case I suggest you move the IFoo definition to a separate
assembly. That would probably get rid of the problem.
This is just a trivial example to display the problem I am
having, not with LoadFrom (it seems to work fine), but with attempting
to treat the returned object as an IFoo.
If you actually read the pages I posted links to, you'd find out that
LoadFrom affects the type identity.
Mattias
--
Mattias Sjögren [MVP] mattias @ mvps.org http://www.msjogren.net/dotnet/
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