reflection question

  • Thread starter Thread starter Antony
  • Start date Start date
A

Antony

Hello - I am wanting to print out a "Yes" next to classes that
implement "Interface01", otherwise a "No". Here is my code. It crashes
with a null reference exception and I am not sure why. Ideas?
Thank you for you help.
Tony


Imports System.Reflection

Public Class Form1
Inherits System.Windows.Forms.Form

''Windows Form Designer generated code

Interface Interface01
End Interface

MustInherit Class Abstract01
End Class

Class Class01
Implements Interface01
End Class

Class Class02
End Class

Class Class03
Inherits Class01
End Class

Class ClassA2
Inherits Abstract01
End Class

Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim asmbly As [Assembly] = [Assembly].GetExecutingAssembly()
Dim asmblyType As Type
For Each asmblyType In asmbly.GetTypes
If asmblyType.BaseType.Equals(GetType(Interface01)) Then
Debug.Write("Yes: ")
Else : Debug.Write("No: ")
End If
Debug.WriteLine(asmblyType.FullName)
Next
End Sub
End Class
 
If asmblyType.BaseType.Equals(GetType(Interface01)) Then
Debug.Write("Yes: ")
Click to expand...

No base type would cause your problem. Use the Type.GetInterfaces()
collection instead.
 
Hi Antony,

Furthermore:

SomeType.BaseType will give you the <class> that SomeType inherited from.
It will never give you an interface as these cannot be inherited.

Regards,
Fergus
 
Hi, an implemented interface isn't a base type, because you can implement as
many interfaces as you want:

Public Class Class01
Implements Interface01
Implements Interface02
 
Thanks Tom.

Just one more thing, if I modify my code (below) it prints out the
names of all classes etc. in a /*project*/. Is it possible to print
out the names of all classes using similar code in a /*solution*/ ?

Thank you
Tony


Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim asmbly As [Assembly] = [Assembly].GetExecutingAssembly
Dim asmblyType As Type
For Each asmblyType In asmbly.GetTypes
Debug.WriteLine(asmblyType.FullName)
Next
End Sub






Tom Spink said:
Hi, an implemented interface isn't a base type, because you can implement as
many interfaces as you want:

Public Class Class01
Implements Interface01
Implements Interface02
.
.
.
Implements Interface99
End Class

So, your code should be:

' /// (See footnotes to convert to VS2002)
Private Sub MySub()
Dim asmThis As [Assembly] = [Assembly].GetExecutingAssembly()
Dim blnFoundInterface As Boolean

For Each typType As Type In asmThis.GetTypes

blnFoundInterface = False

For Each typInterface As Type In typType.GetInterfaces
If typInterface Is GetType(Interface01) Then
blnFoundInterface = True
Exit For
End If
Next

If blnFoundInterface Then
Debug.Write("Yes: ")
Else
Debug.Write("No: ")
End If

Debug.WriteLine(typType.FullName)

Next

End Sub
' ///

--
HTH,
-- Tom Spink, Über Geek

Please respond to the newsgroup,
so all can benefit

" System.Reflection Master "

==== Converting to 2002 ====
Remove inline declarations


Antony schriebt,
: Hello - I am wanting to print out a "Yes" next to classes that
: implement "Interface01", otherwise a "No". Here is my code. It crashes
: with a null reference exception and I am not sure why. Ideas?
: Thank you for you help.
: Tony
:
:
: Imports System.Reflection
:
: Public Class Form1
: Inherits System.Windows.Forms.Form
:
: ''Windows Form Designer generated code
:
: Interface Interface01
: End Interface
:
: MustInherit Class Abstract01
: End Class
:
: Class Class01
: Implements Interface01
: End Class
:
: Class Class02
: End Class
:
: Class Class03
: Inherits Class01
: End Class
:
: Class ClassA2
: Inherits Abstract01
: End Class
:
: Private Sub Button1_Click(ByVal sender As System.Object, _
: ByVal e As System.EventArgs) Handles Button1.Click
: Dim asmbly As [Assembly] = [Assembly].GetExecutingAssembly()
: Dim asmblyType As Type
: For Each asmblyType In asmbly.GetTypes
: If asmblyType.BaseType.Equals(GetType(Interface01)) Then
: Debug.Write("Yes: ")
: Else : Debug.Write("No: ")
: End If
: Debug.WriteLine(asmblyType.FullName)
: Next
: End Sub
: End Class
Click to expand...
 
One Project is one assembly, a solution can contain many assemblies. You'd
have to perform reflection on all referenced assemblies, by dynamically
loading them.

If your project doesn't reference an assembly, (and you are using .NET 1.1)
then you can call [Assembly].LoadFile to load it into an Assembly object,
then run the code on that assembly.

If you are using .NET 1.0, there is the .Load method, which requires the
fully qualified name of the Assembly.

--
HTH,
-- Tom Spink, Über Geek

Please respond to the newsgroup,
so all can benefit

" System.Reflection Master "

==== Converting to 2002 ====
Remove inline declarations


: Thanks Tom.
:
: Just one more thing, if I modify my code (below) it prints out the
: names of all classes etc. in a /*project*/. Is it possible to print
: out the names of all classes using similar code in a /*solution*/ ?
:
: Thank you
: Tony
:
:
: Private Sub Button1_Click(ByVal sender As System.Object, _
: ByVal e As System.EventArgs) Handles Button1.Click
: Dim asmbly As [Assembly] = [Assembly].GetExecutingAssembly
: Dim asmblyType As Type
: For Each asmblyType In asmbly.GetTypes
: Debug.WriteLine(asmblyType.FullName)
: Next
: End Sub
:
:
:
:
:
:
: > Hi, an implemented interface isn't a base type, because you can
implement as
: > many interfaces as you want:
: >
: > Public Class Class01
: > Implements Interface01
: > Implements Interface02
: > .
: > .
: > .
: > Implements Interface99
: > End Class
: >
: > So, your code should be:
: >
: > ' /// (See footnotes to convert to VS2002)
: > Private Sub MySub()
: > Dim asmThis As [Assembly] = [Assembly].GetExecutingAssembly()
: > Dim blnFoundInterface As Boolean
: >
: > For Each typType As Type In asmThis.GetTypes
: >
: > blnFoundInterface = False
: >
: > For Each typInterface As Type In typType.GetInterfaces
: > If typInterface Is GetType(Interface01) Then
: > blnFoundInterface = True
: > Exit For
: > End If
: > Next
: >
: > If blnFoundInterface Then
: > Debug.Write("Yes: ")
: > Else
: > Debug.Write("No: ")
: > End If
: >
: > Debug.WriteLine(typType.FullName)
: >
: > Next
: >
: > End Sub
: > ' ///
: >
: > --
: > HTH,
: > -- Tom Spink, Über Geek
: >
: > Please respond to the newsgroup,
: > so all can benefit
: >
: > " System.Reflection Master "
: >
: > ==== Converting to 2002 ====
: > Remove inline declarations
: >
: >
: > Antony schriebt,
: > : Hello - I am wanting to print out a "Yes" next to classes that
: > : implement "Interface01", otherwise a "No". Here is my code. It crashes
: > : with a null reference exception and I am not sure why. Ideas?
: > : Thank you for you help.
: > : Tony
: > :
: > :
: > : Imports System.Reflection
: > :
: > : Public Class Form1
: > : Inherits System.Windows.Forms.Form
: > :
: > : ''Windows Form Designer generated code
: > :
: > : Interface Interface01
: > : End Interface
: > :
: > : MustInherit Class Abstract01
: > : End Class
: > :
: > : Class Class01
: > : Implements Interface01
: > : End Class
: > :
: > : Class Class02
: > : End Class
: > :
: > : Class Class03
: > : Inherits Class01
: > : End Class
: > :
: > : Class ClassA2
: > : Inherits Abstract01
: > : End Class
: > :
: > : Private Sub Button1_Click(ByVal sender As System.Object, _
: > : ByVal e As System.EventArgs) Handles Button1.Click
: > : Dim asmbly As [Assembly] = [Assembly].GetExecutingAssembly()
: > : Dim asmblyType As Type
: > : For Each asmblyType In asmbly.GetTypes
: > : If asmblyType.BaseType.Equals(GetType(Interface01)) Then
: > : Debug.Write("Yes: ")
: > : Else : Debug.Write("No: ")
: > : End If
: > : Debug.WriteLine(asmblyType.FullName)
: > : Next
: > : End Sub
: > : End Class
 
Hi Tom,

Is there any class which can provide a list of the Assemblies within the
Soloution?

Regards,
Fergus
 
Hi Fergus,

A Solution isn't compiled into anything, a solution has no meaning in .NET,
it is simply a Visual Studio term for a collection of projects. A Project
could be an assembly, e.g. a C#, J#, VB.NET assembly, or it could be
something completely different like a Help File.

So basically, no, because a solution means nothing in .NET.

--
HTH,
-- Tom Spink, Über Geek

Please respond to the newsgroup,
so all can benefit

" System.Reflection Master "

==== Converting to 2002 ====
Remove inline declarations


: Hi Tom,
:
: Is there any class which can provide a list of the Assemblies within
the
: Soloution?
:
: Regards,
: Fergus
:
:
 
Hi Fergus, yes this is what I am looking for too.

I have a "good feeling" about:

For Each aAll As [Assembly] In AppDomain.CurrentDomain.GetAssemblies()
'Code in here
Next

but I can't get it going and my underlying feeling is that Tom is on
the right when he says "No".

Cheers
Tony
 
Hi Tom,

Maybe I should have said 'executable' or 'application' then, for it is the
collection of Assemblies that make up a program that I'm thinking about.

Regards,
Fergus
 
Hi Tony,

Lol, actually this is out of my area but I was asking on your behalf as I
knew that this was what you were after. :-)

Having just seen Tom's answer, I wanted to get in there quick and steer
him right. I do this quite often (in the group generally - not with Tom). This
time I chose to do it as a question but my arrow fell short. :-((

I think the problem with GetAssemblies is that it will get those that have
been loaded so far, not the entire list. I would hope that there's a way to
get them all. It makes good sense that the information is there somewhere but
it may be distributed rather than centralised.

What do you reckon Tom? ;-)

Regards,
Fergus
 
Fergus Cooney said:
Hi Tony,

Lol, actually this is out of my area but I was asking on your behalf as I
knew that this was what you were after. :-)

Having just seen Tom's answer, I wanted to get in there quick and steer
him right. I do this quite often (in the group generally - not with Tom). This
time I chose to do it as a question but my arrow fell short. :-((

I think the problem with GetAssemblies is that it will get those that have
been loaded so far, not the entire list. I would hope that there's a way to
get them all. It makes good sense that the information is there somewhere but
it may be distributed rather than centralised.
Click to expand...

Well, might as well through my hat into the ring as I've recently worked
with reflection.

Now, regarding the first question of a collection of the assemblies that
make up an "application" being stored somewhere, Tom's answer is dead on.
Or at least I think the best way to accomplish the task with the way most
people program. That is, you have a primary executable which may call a
series of libraries held in other assemblies. These are all usually loaded
at executation of the main assembly. The only time its not, is if your
doing something like modular coding where you use reflection to dynmiaclly
load assemblies at different times in the programs lifecycle.

If that is true, you could always recusivly push through each reference of
the primary assembly. Use GetReferencedAssemblies and
GetSatelliteAssemblies (if needed). Which both return collections of
assembly references. So, unless you are dynamically invoking methods your
program knows absolutly nothing about from assemblies it knows absolutly
nothing about, (I mean no interfaces either, kinda like a really really
really dynamic unit tester... hmmmmm.. interesting idea). there should be
no need other than those two methods. And as said, going through them
recursivly will tell you every single assembly you want to know about.

Hope it helps, keep the peace, and keep on rockin in the freeworld ted
nugent style.

-CJ
 
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