Web Development

Imports System<br />
Imports System.Web.Caching<br />
Imports System.Reflection<br />
<br />
Namespace INVID.DNN.Modules.HelloWorld.Data<br />
<br />
Public MustInherit Class DataProvider<br />
<br />
#Region "Shared/Static Methods"<br />
' singleton reference to the instantiated object<br />
Private Shared objProvider As DataProvider = Nothing<br />
<br />
' constructor<br />
Shared Sub New()<br />
CreateProvider()<br />
End Sub<br />
<br />
' dynamically create provider<br />
' This sub gets called, It is calling the methods that will raise the exception<br />
Private Shared Sub CreateProvider()<br />
objProvider = CType(Framework.Reflection.CreateObject( _<br />
"data", _<br />
"INVID.DNN.Modules.HelloWorld.Data", _<br />
"INVID.DNN.Modules.HelloWorld"), DataProvider)<br />
End Sub<br />
<br />
' return the provider<br />
Public Shared Shadows Function Instance() As DataProvider<br />
Return objProvider<br />
End Function<br />
#End Region<br />
End Class<br />
End Namespace

' dynamically create an object from a TypeName using a CacheKey<br />
Public Shared Function CreateObject(ByVal TypeName As String, _<br />
ByVal CacheKey As String) As Object<br />
<br />
If CacheKey = "" Then<br />
CacheKey = TypeName<br />
End If<br />
<br />
' use the cache for performance<br />
Dim objType As Type = CType(DataCache.GetCache(CacheKey), Type)<br />
<br />
' is the type in the cache?<br />
If objType Is Nothing Then<br />
Try<br />
' use reflection to get the type of the class<br />
objType = Type.GetType(TypeName, True)<br />
' insert the type into the cache<br />
DataCache.SetCache(CacheKey, objType)<br />
Catch exc As Exception<br />
' could not load the type<br />
LogException(exc)<br />
End Try<br />
End If<br />
' dynamically create the object<br />
Return Activator.CreateInstance(objType) ' This line raises the error mentioned before<br />
End Function