Comparing same interface type returns false, Why?

[Joe Black]

Hi all,

Using Windows CP Pro
VS .net 2005

I'm creating an app that allows user to extend its functionality by
installing plug in modules, these modules support an interface I have
created called IPlugInInterfac e. The problem is when I come to load them
I check each dll to see if supports this interface, they all return
false even though when I inspect them during debugging they look the
same, I use the following function:

public ArrayList SearchPath(stri ng dir, AppDomain domain)
{
ArrayList ar = new ArrayList();

foreach (string File in System.IO.Direc tory.GetFiles(d ir, "*.dll"))
{
try
{
Type ct = typeof(TestName space.PlugIn.IP lugInInterface) ;
System.Reflecti on.Assembly asm =
System.Reflecti on.Assembly.Loa dFrom(File);

foreach (Type t in asm.GetTypes())
{
foreach (Type iface in t.GetInterfaces ())
{
//*************** *************** *
// see text below
//*************** *************** *
if (ct.IsAssignabl eFrom(iface))
{
ar.Add(t);
break;
}
}
}
}
catch (Exception ex)
{
}
}
return ar;
}
//*************** ***

this is where the problem occurs, if I inspect both ct and iface both
seem to be of the same type, ie namespace and name etc but the call to
IsAssignableFro m always returns false.

Any ideas

TIA

Joe

[Ming Chen]

Hi, Joe.

The plug in classes would have to implement the exact same interface, not
only the namespace qualified interface name, but also the same assembly and
version. Check AssemblyQualifi edName property of both types, they have to be
the same for IsAssignableFro m to return true.

--
Ming Chen
http://engdump.blogspot.com/
"Joe Black" <Jo******@newsg roup.nospam> wrote in message
news:eX******** ******@TK2MSFTN GP14.phx.gbl...

Hi all,

Using Windows CP Pro
VS .net 2005

I'm creating an app that allows user to extend its functionality by
installing plug in modules, these modules support an interface I have
created called IPlugInInterfac e. The problem is when I come to load them I
check each dll to see if supports this interface, they all return false
even though when I inspect them during debugging they look the same, I use
the following function:

public ArrayList SearchPath(stri ng dir, AppDomain domain)
{
ArrayList ar = new ArrayList();

foreach (string File in System.IO.Direc tory.GetFiles(d ir, "*.dll"))
{
try
{
Type ct = typeof(TestName space.PlugIn.IP lugInInterface) ;
System.Reflecti on.Assembly asm =
System.Reflecti on.Assembly.Loa dFrom(File);

foreach (Type t in asm.GetTypes())
{
foreach (Type iface in t.GetInterfaces ())
{
//*************** *************** *
// see text below
//*************** *************** *
if (ct.IsAssignabl eFrom(iface))
{
ar.Add(t);
break;
}
}
}
}
catch (Exception ex)
{
}
}
return ar;
}
//*************** ***

this is where the problem occurs, if I inspect both ct and iface both seem
to be of the same type, ie namespace and name etc but the call to
IsAssignableFro m always returns false.

Any ideas

TIA

Joe

[Joe Black]

Ming Chen wrote:

Hi, Joe.

The plug in classes would have to implement the exact same interface, not
only the namespace qualified interface name, but also the same assembly and
version. Check AssemblyQualifi edName property of both types, they have to be
the same for IsAssignableFro m to return true.

Hi Ming,

I have the interface declared within an external DLL file as follows

public interface IPlugInInterfac e
{
#region Variable declaration

int PlugInType { get;}
string PlugInName { get;}
string PlugInDescripti on { get;}
string PlugInShortDesc ription { get;}
int PlugInMajorVers ion { get;}
int PlugInMinorVers ion { get;}
char PlugInRevision { get;}
string PlugInGuid { get;}
string PlugInReleaseDa te { get;}
string PlugInAuthor { get;}
string PlugInAuthorInf ormation { get;}
bool RequiresRegistr ation { get;}

#endregion

#region Member function declaration

void PerformAction(I PlugInContext context);
void ShowForm(System .Windows.Forms. Control parent);

#endregion
}

I then declare my class:

public class MyPlugin:IPlugI nInterface
{
//code goes here
}

Does this not mean I am using the exact same interface, or am I missing
something?

Your help is appreciated.

Joe

[Ming Chen]

You have to declare the interface in a single assembly for all PlugIns and
having all other assemblies reference to this one. .NET class/interface have
their own internal type identifier hence they are not simply matched base on
memory layout. Types declared in different dlls are different types even if
their definitions are exactly the same.

For example, you can create a dll (PluginInterfac e.dll) which contains
nothing but the definition of the interface, then create individual PlugIn
classes by adding reference to this dll.

--
Ming Chen
http://engdump.blogspot.com/
"Joe Black" <Jo******@newsg roup.nospam> wrote in message
news:OA******** *****@TK2MSFTNG P15.phx.gbl...

Ming Chen wrote:

Hi, Joe.

The plug in classes would have to implement the exact same interface,
not only the namespace qualified interface name, but also the same
assembly and version. Check AssemblyQualifi edName property of both types,
they have to be the same for IsAssignableFro m to return true.

Hi Ming,

I have the interface declared within an external DLL file as follows

public interface IPlugInInterfac e
{
#region Variable declaration

int PlugInType { get;}
string PlugInName { get;}
string PlugInDescripti on { get;}
string PlugInShortDesc ription { get;}
int PlugInMajorVers ion { get;}
int PlugInMinorVers ion { get;}
char PlugInRevision { get;}
string PlugInGuid { get;}
string PlugInReleaseDa te { get;}
string PlugInAuthor { get;}
string PlugInAuthorInf ormation { get;}
bool RequiresRegistr ation { get;}

#endregion

#region Member function declaration

void PerformAction(I PlugInContext context);
void ShowForm(System .Windows.Forms. Control parent);

#endregion
}

I then declare my class:

public class MyPlugin:IPlugI nInterface
{
//code goes here
}

Does this not mean I am using the exact same interface, or am I missing
something?

Your help is appreciated.

Joe

[Joe Black]

Ming Chen wrote:

You have to declare the interface in a single assembly for all PlugIns and
having all other assemblies reference to this one. .NET class/interface have
their own internal type identifier hence they are not simply matched base on
memory layout. Types declared in different dlls are different types even if
their definitions are exactly the same.

For example, you can create a dll (PluginInterfac e.dll) which contains
nothing but the definition of the interface, then create individual PlugIn
classes by adding reference to this dll.

Thanks Ming,

I found that I had a copy of the dll that implemented the
IPlugInInterfac e in the same directory that the dll with the actual plug
in was in, this seemed to cause the appdomain to look at that copy of
the IPlugInInterfac e, hence the failure of the function call.

Many thanks for your help

Joe

[Ashura]

hi, plz try the following (it always works 4 me)

Type _type = somePlugIn.GetT ype();

foreach (Type iface in _type.GetInterf aces()) {
if (iface == typeof(IPlugInI nterface)) {
//do some magic
}
}

regards