Hi there,
I have an interface (called AuthenticationI nterface) shown below:
Public Interface AuthenticationI nterface
Function IsLoggedIn() As Boolean
Function Authenticate(By Val User As LinkDirectoryUs er) As Boolean
Function GetCurrentUser( ) As LinkDirectoryUs er
Function IsUserSuspended (ByVal User As LinkDirectoryUs er) As
Boolean
Function GetAllRoles() As String()
Sub Register(ByVal User As LinkDirectoryUs er)
Sub Logout()
Sub DeleteUser(ByVa l User As LinkDirectoryUs er)
Sub SuspendUser(ByV al User As LinkDirectoryUs er)
Sub UpdateUser(ByVa l User As LinkDirectoryUs er)
End Interface
And I use the following code to load a type that implements that
interface based on the value of the web.config file:
Public Function Current() As Object
Dim asm As String = HttpContext.Cur rent.Server.Map Path("bin\"
& ConfigurationSe ttings.AppSetti ngs("Authentica tionProvider"))
Dim objDll As [Assembly] = [Assembly].LoadFrom(asm)
For Each t As Type In objDll.GetTypes
If t.IsPublic Then
If Not ((t.Attributes And TypeAttributes. Abstract) =
TypeAttributes. Abstract) Then
Dim objInterface As Type =
t.GetInterface( "Authentication Interface", True)
If Not objInterface Is Nothing Then
Dim objPlugin As Object =
objDll.CreateIn stance(t.FullNa me)
Return objPlugin
End If
End If
End If
Next
End Function
As you can see this returns an object, this is because I get casting
errors when trying to convert the object to a AuthenticationI nterface
(but I can still use the object perfectly), my question is how can I
convert the object loaded to a AuthenticationI nterface without causing
a cast error?
Thanks loads, Martin.
6  1348 
Hello Martin,
I'm not familiar with VB, but Ill take a stab at this...
Public Function Current() As AuthenticationI nterface
Dim asmPath As String = HttpContext.Cur rent.Server.Map Path("bin\" & ConfigurationSe ttings.AppSetti ngs("Authentica tionProvider"))
Dim asm As [Assembly] = [Assembly].LoadFrom(asmPa th)
For Each t As Type in asm.GetExported Types()
If t.IsAssignableF rom(TypeOf(Auth enticationInter face)) ' This may
be TypeOf(Authenti cationInterface ).IsAssignableF rom(t)
Return Activator.Creat eInstance(t)
End If
Next
End Function
--
Matt Berther http://www.mattberther.com Hi there,
I have an interface (called AuthenticationI nterface) shown below:
Public Interface AuthenticationI nterface
Function IsLoggedIn() As Boolean
Function Authenticate(By Val User As LinkDirectoryUs er) As Boolean
Function GetCurrentUser( ) As LinkDirectoryUs er
Function IsUserSuspended (ByVal User As LinkDirectoryUs er) As
Boolean
Function GetAllRoles() As String()
Sub Register(ByVal User As LinkDirectoryUs er)
Sub Logout()
Sub DeleteUser(ByVa l User As LinkDirectoryUs er)
Sub SuspendUser(ByV al User As LinkDirectoryUs er)
Sub UpdateUser(ByVa l User As LinkDirectoryUs er)
End Interface
And I use the following code to load a type that implements that
interface based on the value of the web.config file:
Public Function Current() As Object
Dim asm As String = HttpContext.Cur rent.Server.Map Path("bin\"
& ConfigurationSe ttings.AppSetti ngs("Authentica tionProvider"))
Dim objDll As [Assembly] = [Assembly].LoadFrom(asm)
For Each t As Type In objDll.GetTypes
If t.IsPublic Then
If Not ((t.Attributes And TypeAttributes. Abstract) =
TypeAttributes. Abstract) Then
Dim objInterface As Type =
t.GetInterface( "Authentication Interface", True)
If Not objInterface Is Nothing Then
Dim objPlugin As Object =
objDll.CreateIn stance(t.FullNa me)
Return objPlugin
End If
End If
End If
Next
End Function
As you can see this returns an object, this is because I get casting
errors when trying to convert the object to a AuthenticationI nterface
(but I can still use the object perfectly), my question is how can I
convert the object loaded to a AuthenticationI nterface without causing
a cast error?
Thanks loads, Martin.
Hello Martin,
I think I misunderstood your problem...
How about instead of
Return objPlugin
do
Return CType(objPlugin , AuthenticationI nterface)
--
Matt Berther http://www.mattberther.com Hi there,
I have an interface (called AuthenticationI nterface) shown below:
Public Interface AuthenticationI nterface
Function IsLoggedIn() As Boolean
Function Authenticate(By Val User As LinkDirectoryUs er) As Boolean
Function GetCurrentUser( ) As LinkDirectoryUs er
Function IsUserSuspended (ByVal User As LinkDirectoryUs er) As
Boolean
Function GetAllRoles() As String()
Sub Register(ByVal User As LinkDirectoryUs er)
Sub Logout()
Sub DeleteUser(ByVa l User As LinkDirectoryUs er)
Sub SuspendUser(ByV al User As LinkDirectoryUs er)
Sub UpdateUser(ByVa l User As LinkDirectoryUs er)
End Interface
And I use the following code to load a type that implements that
interface based on the value of the web.config file:
Public Function Current() As Object
Dim asm As String = HttpContext.Cur rent.Server.Map Path("bin\"
& ConfigurationSe ttings.AppSetti ngs("Authentica tionProvider"))
Dim objDll As [Assembly] = [Assembly].LoadFrom(asm)
For Each t As Type In objDll.GetTypes
If t.IsPublic Then
If Not ((t.Attributes And TypeAttributes. Abstract) =
TypeAttributes. Abstract) Then
Dim objInterface As Type =
t.GetInterface( "Authentication Interface", True)
If Not objInterface Is Nothing Then
Dim objPlugin As Object =
objDll.CreateIn stance(t.FullNa me)
Return objPlugin
End If
End If
End If
Next
End Function
As you can see this returns an object, this is because I get casting
errors when trying to convert the object to a AuthenticationI nterface
(but I can still use the object perfectly), my question is how can I
convert the object loaded to a AuthenticationI nterface without causing
a cast error?
Thanks loads, Martin.
Sorry if I confused you, I get a casting error:
Specified cast is not valid.
Description: An unhandled exception occurred during the execution of
the current web request. Please review the stack trace for more
information about the error and where it originated in the code.
Exception Details: System.InvalidC astException: Specified cast is not
valid.
When trying to convert it into the interface, Thanks for the help,
martin.
Hello mc******@gmail. com,
Can you post the exact snippet of code that causes this error?
--
Matt Berther http://www.mattberther.com Sorry if I confused you, I get a casting error:
Specified cast is not valid.
Description: An unhandled exception occurred during the execution of
the current web request. Please review the stack trace for more
information about the error and where it originated in the code.
Exception Details: System.InvalidC astException: Specified cast is not
valid.
When trying to convert it into the interface, Thanks for the help,
martin.
I have.... I get it when trying to convert the output of that function
into the interface
Hello mc******@gmail. com,
I imagine that using your posted code, the code that generates the cast error
looks something like this?
Dim myObj As Object = someClass.Curre nt()
Dim authInterface As AuthenticationI nterface = CType(myObj, AuthenticationI nterface)
This should work... If not, you might look at DirectCast instead of CType.
In C#, you would do:
AuthenticationI nterface authInterface = (Authentication Interface)someC lass.Current();
and I believe the equivalent to that is CType.
--
Matt Berther http://www.mattberther.com I have.... I get it when trying to convert the output of that function
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