I'm toying around with a 3rd party library and something has me absolutely puzzled.
When I instantiate this class, immediately all of the properties of the class throw exceptions before any more code even runs. Why is this happening? It's not just this TypedSegmentPWK class, it's all of the typedsegment classes.. of which there are many.
Simple instantiation fails
Imports OopFactory.X12.Parsing
Imports OopFactory.X12.Parsing.Model
Imports OopFactory.X12.Parsing.Model.Typed
....
Dim test As New TypedSegmentPWK
test.PWK04_EntityIdentifierCode = "blah"
Assigning a value to PWK04_EntityIdentifierCode or any other property of test fails with a null reference exception.
TypedSegmentPWK:
Namespace OopFactory.X12.Parsing.Model.Typed
Public Class TypedSegmentPWK
Inherits TypedSegment
Public Sub New()
Public Property PWK01_ReportTypeCode As String
Public Property PWK02_ReportTransmissionCode As String
Public Property PWK03_ReportCopiesNeeded As Integer?
Public Property PWK04_EntityIdentiferCodeEnum As EntityIdentifierCode
Public Property PWK04_EntityIdentifierCode As String
Public Property PWK05_IdentificationCodeQualifier As String
Public Property PWK05_IdentificationCodeQualifierEnum As IdentificationCodeQualifier
Public Property PWK06_IdentificationCode As String
Public Property PWK07_Description As String
Public Property PWK08_ActionsIndicated As String
Public Property PWK09_RequestCategoryCode As String
End Class
End Namespace
TypedSegment:
Namespace OopFactory.X12.Parsing.Model
Public MustInherit Class TypedSegment
Protected Sub New(segmentId As String)
Public Event Initialized As EventHandler
Public Event Initializing As EventHandler
Protected Overridable Sub OnInitialized(e As EventArgs)
Protected Overridable Sub OnInitializing(e As EventArgs)
End Class
End Namespace
Full source here: https://github.com/KeyMarkInc/OopFactory.X12
All the properties reference _segment defined in TypedSegment, e.g.
public string PWK04_EntityIdentifierCode
{
get { return _segment.GetElement(4); }
set { _segment.SetElement(4, value); }
}
However, the _segment variable is not initialized until TypedSegment.Initialize(Container parent, X12DelimiterSet delimiters) is called...
internal void Initialize(Container parent, X12DelimiterSet delimiters)
{
OnInitializing(new EventArgs());
_segment = new Segment(parent, delimiters, _segmentId);
OnInitialized(new EventArgs());
}
This is an internal method, so presumably something in this framework is supposed to call it, and not you as the user. So, I would guess the answer is that you are using the TypedSegmentPWK class incorrectly, although I don't know what the correct way is.
Related
I have a DLL file created in VB6. It contains a class named Product and that contains the following simple code:
Option Explicit
Private sDescription As String
Public Property Get Description() As String
Description = sDescription
End Property
Public Property Let Description(Value As String)
sDescription = Value
End Property
I want to use this DLL in VB.NET, which is nothing more than registering the DLL on my system and including the DLL file in the references. Visual Studio automatically generates an interop DLL to consume the COM DLL. This interop DLL generates interfaces for all classes. In VB.NET I want to create a new class that implements the Product interface from the interop DLL. So I code:
Imports myAssembly
Public Class NetProduct
Implements myAssembly.Product
Public Property Description As String Implements _Product.Description
Get
Throw New NotImplementedException()
End Get
Set(value As String)
Throw New NotImplementedException()
End Set
End Property
End Class
The property is auto-generated because I implemented the Product interface. But here comes the problem because when I start using the NetProduct class I get an error telling me this:
Method 'set_Description' in type 'myProject.NetProduct' from
assembly 'myProject, Version=1.0.0.0, Culture=neutral,
PublicKeyToken=null' does not have an implementation.
The problem is that there is no method set_Description in the interface. When I view the definition of the Product interface it shows me the following:
Imports System.Runtime.InteropServices
Namespace myAssembly
<CoClass(GetType(ProductClass))> <Guid("49CE2F98-931C-441B-B322-9F39B6D6F212")>
Public Interface Product
Implements _Product
End Interface
End Namespace
The definition of the _Product interface is:
Imports System.Runtime.InteropServices
Namespace myAssembly
<Guid("49CE2F98-931C-441B-B322-9F39B6D6F212")> <TypeLibTypeAttribute(4304)>
Public Interface _Product <DispId(1745027072)>
Property Description As String
End Interface
End Namespace
When I use the interface myAssembly.Product directly to create a new object then everything works as you would expect. The property does not pose a problem there. But when I implement the interface in a .NET class the problem arises.
How do I solve this?
[update 1] After creating a method Set_Description I see the following error appear:
property 'Description' implicitly defines 'set_Description', which
conflicts with a member of the same name in class 'NetProduct'.
This must have something to do with my problem, although I don't know what it is. I already tried completing the property to make sure the Throw New NotImplementedException() wouldn't be in the way but that didn't make the error go away. My code builds just fine by the way. The error I gave earlier is a runtime error. Not a build error.
Private myDescription As String
Public Property Description As String Implements Product.Description
Get
Return myDescription
End Get
Set(value As String)
myDescription = value
End Set
End Property
[update 2] I have used JetBrains DotPeek to disassemble the interop.dll that Visual Studio generates. Disassembly is coded in C#. It contains 2 interfaces and 1 class for the single Product class from VB6. Here are all details.
I'll start with the Product class itself.
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace myAssembly
{
[ClassInterface(0)]
[Guid("C54B96A8-1499-4B76-8508-0B732E551326")]
[TypeLibType(2)]
[ComImport]
public class ProductClass : _Product, Product
{
[MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
public extern ProductClass();
[DispId(1745027072)]
public virtual extern string Description { [DispId(1745027072), MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)] [return: MarshalAs(UnmanagedType.BStr)] get; [DispId(1745027072), MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)] [param: MarshalAs(UnmanagedType.BStr), In, Out] set; }
}
}
The ProductClass uses 2 interfaces. I don't understand why because one of those is just an implementation of the other. This is the Product interface.
using System.Runtime.InteropServices;
namespace myAssembly
{
[CoClass(typeof (ProductClass))]
[Guid("49CE2F98-931C-441B-B322-9F39B6D6F212")]
[ComImport]
public interface Product : _Product
{
}
}
And then we have the _Product interface. They even share the same Guid. It might have something to do with backwards compatibility.
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace myAssembly
{
[Guid("49CE2F98-931C-441B-B322-9F39B6D6F212")]
[TypeLibType(4304)]
[ComImport]
public interface _Product
{
[DispId(1745027072)]
string Description { [DispId(1745027072), MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)] [return: MarshalAs(UnmanagedType.BStr)] get; [DispId(1745027072), MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)] [param: MarshalAs(UnmanagedType.BStr), In, Out] set; }
}
}
This is all I could find. Still no clue where the error for Set_Description comes from.
[Update 3] Example code
The code for the VB6 class is on top of this question. Nothing fancy there. The code for testing implementation in .NET is like this:
Imports myAssembly
Public Class NetProduct
Implements myAssembly.Product
Private myDescription As String
Public Property Description As String Implements Product.Description
Get
Return myDescription
End Get
Set(value As String)
myDescription = value
End Set
End Property
End Class
To test the NetProduct class I dropped a Button on a Form and create an instance of the class when the button is being clicked.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click '<- Error happens here, so on loading the datatype!
Dim Product As New NetProduct 'Error does NOT happen here.
End Sub
The whole project compiles without errors. The project even runs without errors UNTIL you click the button. Probably because the NetProduct type is first loaded on that point.
I used a console app to do my test. Other than that, my VB.NET code is basically identical to yours in update 3. The VB.NET properties were auto-generated by VS with the stub Throw New NotImplementedException() after using the Implements statement :
Imports OurCOMDll
Class TestClass
Implements OurCOMDll.ClassInCOMDll
Dim msStringProperty As String = String.Empty
Public Property StringProperty As String Implements _ClassInCOMDll.StringProperty
Get
StringProperty= msStringProperty
End Get
Set(value As String)
msStringProperty = value
End Set
End Property
End Class
Module Module1
Sub Main()
Dim o As New OurCOMDll.ClassInCOMDll
o.StringProperty = "Hello World!"
Console.WriteLine(o.StringProperty) ' Outputs 'Hello World!' as expected
Console.ReadLine()
End Sub
End Module
Same is true for the VB6 code. The string property is implemented like yours.
Distinguishing factors so far:
VS 2019 vs. VS 2017
(Consuming) GUI vs. Console application
Different property names
Is there a way to write an Audit log automatically?
I have created a DbSet(Of Protocols)
Here is my protocol class:
Public Class Protocol
Inherits ModelBase
Implements ILogicalTimestamp
<Key>
Public Property ProtocolId As Integer
<Required>
Public Property ProtocolText As String
Public Property CreatedByUserId As Integer?
<Required>
Public Property CreatedByUser As User
<Required>
<DefaultValue(0)>
Public Property Type As ProtocolType
Public Property LinkedToUserId As Integer?
Public Property LinkedToUser As User
Public Property LinkedToBusinessPartnerId As Integer?
Public Property LinkedToBusinessPartner As BusinessPartner
Public Property LinkedToClientId As Integer?
Public Property LinkedToClient As Client
Public Property LinkedToSettingId As Integer?
Public Property LinkedToSetting As Setting
Public Property LastUpdateTimestamp As Date? Implements ILogicalTimestamp.LastUpdateTimestamp
Public Property CreationTimestamp As Date? Implements ILogicalTimestamp.CreationTimestamp
Public Enum ProtocolType
AutoChanges = 0
Explicitly = 1
End Enum
End Class
How can i write changes in protocol?
And how can i get the current UserId into the SaveChanges method to fill CreatedByUserId property in my protocol class?
Maybe anyone has an idea to do that automatically.
You can create a custom DB Context inheriting from DbContext, and then override the SaveChanges() method, so you can manipulate the data before/after modification.
Or you can use a library like Audit.EntityFramework, or check its code (C# sorry).
Also the library EntityFramework-Plus can probably help.
I would like to write an interface class and use it like this
public Interface IFunction
property name as string
end interface
public class ModelFunction
implements IFunction
public property name as string
public sub new()
end class
*EDIT(deleted following sentence for being noob, thanks #damien_the_unbeliever for pointing this out):But this is not possible to get because a property in an vb.net interface has to be readonly or writeonly (as far as i get it)*
I have now written this but seems a little wrong:
public Interface IFunction
Readlonly property getName() as string
writeonly property writeName() as string
end interface
public class ModelFunction
implements IFunction
....
end class
Anyone have a better solution for this? or can help me out with properties in an Interface class. Have read some articles here on stackoverflow but none of them point me in the right direction.
This works fine for me:
Public Class Class1
Implements Thing
Property Gary As Int32 Implements Thing.Gary
Get
Return 10
End Get
Set(value As Int32)
End Set
End Property
End Class
Public Interface Thing
Property Gary As Int32
End Interface
There's even an example on the documentation page for Interface:
Interface IAsset
Event ComittedChange(ByVal Success As Boolean)
Property Division() As String
Function GetID() As Integer
End Interface
I am normally a c# programmer but am now working in VB for this one project when I use to set up a singleton class I would follow the Jon Skeet model
public sealed class Singleton
{
static Singleton instance = null;
static readonly object padlock = new object();
Singleton()
{
}
public static Singleton Instance
{
get
{
lock (padlock)
{
if (instance == null)
{
instance = new Singleton();
}
return instance;
}
}
}
//Added to illustrate the point
public static void a()
{
}
public void b()
{
}
}
or one of the variations now if I write the statement in c#
Singleton.Instance What procedures is all of the members that are not static, b but not a.
Now when I do the same in VB
Private Shared _instance As StackTracker
Private Shared ReadOnly _lock As Object = New Object()
Private Sub New()
_WorkingStack = New Stack(Of MethodObject)
_HistoryStack = New Queue(Of MethodObject)
End Sub
Public Shared ReadOnly Property Instance() As StackTracker
Get
SyncLock _lock
If (_instance Is Nothing) Then
_instance = New StackTracker()
End If
End SyncLock
Return _instance
End Get
End Property
I get StackTracker.Instance.Instance and it keeps going, while it is not the end of the world it looks bad.
Question is there a way in VB to hide the second instance so the user can not recursively call Instance?
Here's the full code:
Public NotInheritable Class MySingleton
Private Shared ReadOnly _instance As New Lazy(Of MySingleton)(Function() New
MySingleton(), System.Threading.LazyThreadSafetyMode.ExecutionAndPublication)
Private Sub New()
End Sub
Public Shared ReadOnly Property Instance() As MySingleton
Get
Return _instance.Value
End Get
End Property
End Class
Then to use this class, get the instance using:
Dim theSingleton As MySingleton = MySingleton.Instance
The original question was not about how to implement the singleton pattern, but referring to the fact that in C# it's a compiler error to try to access a static member via an instance. In the current VB it's a warning.
Solution:
You can change the project compiler settings to "Treat all warnings as errors", but I don't know any way to explicitly treat just warning 42025 as an error.
That being said, there is also a much simpler way to implement singletons in VB:
public class Singleton
private sub new()
end sub
public shared readonly property Instance as Singleton
get
static INST as Singleton = new Singleton
return INST
end get
end property
end class
This relies on VB thread-safe single initialization of static variables which is a feature not found in C#. The line of code beginning with the word "static" is only evaluated once even if the Instance property is accessed many times from many threads.
This is actually not the proposal put forth by Jon. You implemented the third version referenced in the article on the matter, which he points out doesn't work according to the EMCA spec due to lack of memory barriers.
Rather, you should work with the fifth version, which uses a nested class and performs the assignment of the instance in the declaration of the static field on the nested class.
If you are working in .NET 4.0, then you don't have to do any of this. You can create a static readonly field of type Lazy<T>, passing LazyThreadSafetyMode.ExecutionAndPublication to the constructor (along with your Func<T> to indicate how to create the instance) to guarantee that the value will only be created once.
Then, you expose a property which simply calls the Lazy<T>.Value property to return the lazy-loaded singleton value.
Maybe I'm missing something but I just do some variation on this, depending on what else is going on in the class:
Class MySingleton
'The instance initializes once and persists (provided it's not intentionally destroyed)
Private Shared oInstance As MySingleton = New MySingleton
'A property initialized via the Create method
Public Shared Property SomeProperty() As Object = Nothing
'Constructor cannot be called directly so prevents external instantiation
Private Sub New()
'Nothing to do
End Sub
'The property returns the single instance
Public Shared ReadOnly Property Instance As MySingleton
Get
Return oInstance
End Get
End Property
'The method returns the single instance while also initializing SomeProperty
Public Shared Function Create(
ByVal SomeParam As Object) As MySingleton
_SomeProperty = SomeParam
Return oInstance
End Function
End Class
Obviously, you would usually only provide either the Instance property or the Create method, not both (though you could if you wanted to for some reason).
In its simplest form it's:
Class MySingleton
Private Shared oInstance As MySingleton = New MySingleton
Private Sub New()
End Sub
Public Shared ReadOnly Property Instance As MySingleton
Get
Return oInstance
End Get
End Property
End Class
I'm creating a domain model where entities often (but not always) have a member of type ActionLog.
ActionLog is a simple class which allows for an audit trail of actions being performed on an instance. Each action is recorded as an ActionLogEntry instance.
ActionLog is implemented (approximately) as follows:
public class ActionLog
{
public IEnumerable<ActionLogEntry> Entries
{
get { return EntriesCollection; }
}
protected ICollection<ActionLogEntry> EntriesCollection { get; set; }
public void AddAction(string action)
{
// Append to entries collection.
}
}
What I would like is to re-use this class amongst my entities and have the entries map to different tables based on which class they are logged against. For example:
public class Customer
{
public ActionLog Actions { get; protected set; }
}
public class Order
{
public ActionLog Actions { get; protected set; }
}
This design is suitable for me in the application, however I can't see a clear way to map this scenario to a database with NHibernate.
I typically use Fluent NHibernate for my configuration, but I'm happy to accept answers in more general HBM xml.
I was having the same problem and was about the post the same question hoping for an answer - but I found the solution with the help of the NH IRC channel on FreeNode.
My scenario has a Document. Various things will have Documents - like Reports, Items, etc. The only difference between Report.Documents and Item.Documents is that the document has a reference to its owner, and it is mapped to a different table.
The solution for this situation is mostly accomplished through .Net. Though - I don't think this solution would be possible with XML mappings.
The Document Class:
Public Class Document
Public Overridable Property DocumentId As Integer
Public Overridable Property Directory As String
Public Overridable Property Name As String
Public Overridable Property Title As String
Public Overridable Property Revision As String
Public Overridable Property Description As String
Public Overridable Property Owner As String
Public Overridable Property UploadedBy As String
Public Overridable Property CreationDate As Date
Public Overridable Property UploadDate As Date
Public Overridable Property Size As Int64
Public Overridable Property Categories As String
End Class
Then we inherit from this class for each of our additional Document types:
Public Class ReportDocument
Inherits Document
Public Overridable Property Report As Report
End Class
Public Class ItemDocument
Inherits Document
Public Overridable Property Item As Item
End Class
Here's where the "magic" happens. We're going to create a generic mapping that requires that the object being used inherits the Document class. This way, Fluent NHibernate can still find all the properties on the objects that inherit from the Document.
Public Class GenericDocumentMapping(Of T As Document)
Inherits ClassMap(Of T)
Public Sub New()
Id(Function(x) x.DocumentId)
Map(Function(x) x.Directory)
Map(Function(x) x.Name)
Map(Function(x) x.Title).Not.Nullable()
Map(Function(x) x.Revision)
Map(Function(x) x.Description)
Map(Function(x) x.Owner)
Map(Function(x) x.UploadedBy)
Map(Function(x) x.CreationDate).Not.Nullable()
Map(Function(x) x.UploadDate).Not.Nullable()
Map(Function(x) x.Size)
Map(Function(x) x.Categories)
End Sub
End Class
You'll notice that this class has no reference to which table it is being mapped to, nor the parent object that each different version will use. Now, we use this generic mapping for each of our special types, and specify the table and map the parent object we created in each class type we created.
Public Class ReportDocumentMapping
Inherits GenericDocumentMapping(Of ReportDocument)
Public Sub New()
MyBase.New()
References(Function(x) x.Item).Column("ReportID")
Table("ReportDocuments")
End Sub
End Class
Public Class ItemDocumentMapping
Inherits GenericDocumentMapping(Of ItemDocument)
Public Sub New()
MyBase.New()
References(Function(x) x.Item).Column("ItemID")
Table("ItemDocuments")
End Sub
End Class
I think this method reduces a lot of code. Now, if you want to make sweeping changes to the document type - you only have to modify the Document class, and the GenericDocumentMapping class.
In my situation - I also just map Documents to a specific table. This is done the same way as the others - inherit from the GenericDocumentMapping and specify the table. The only difference is I don't reference a parent object.
Public Class DocumentMapping
Inherits GenericDocumentMapping(Of Document)
Public Sub New()
MyBase.New()
Table("Documents")
End Sub
End Class
youu can use join to map it to more than table