Can a class be removed by code - c#

I have a query whether there is any sensible (pinch of salt needed here) mechanism to 'remove' a class from my codebase.
I'm not trying to delete a .cs file here, I'm trying to kind of 'null out' a class.
I'm looking for something which does something along the lines of 'un-declaring' a class definition.
The reason for this slightly odd request idea is that I have a PCL with some shared entities. These entities are used by SQLite and in the PCL library I've defined the SQLite [PrimaryKeyAttribute] property so that I can mark the entities PKs.
In my consuming library I have SQLite for Windows Runtime installed and 'sqlite-net' for the linq like wrapper. It's in this wrapper that the [PrimaryKeyAttribute] is defined.
What I was hoping to do was define the [PrimaryKeyAttribute] class as below in the PCL library:
namespace SQLite
{
[AttributeUsage(AttributeTargets.Property)]
public class PrimaryKeyAttribute : Attribute
{
}
}
But the problem with that is that it's overwritten by the same definition in the consuming library. Things work happily if I comment out the attribute from the definition in the consuming library, but as soon as I (or someone else) updates the sqlite-net package we're going to hit a load of issues as the data access will fall over.
I suppose I'm looking for a kind of 'do not compile' flag of some form which I can apply to code in a different file. Any ideas/thoughts on this one?

Related

How to hide C# class from custom IL Inspector?

I am currently working with a piece of software known as Kofax TotalAgility or KTA for short.
This is Business Process Automation Software, which I have the "pleasure" of expanding with custom .net libraries.
I have been creating a MS Graph library to perform actions with the MS Graph API. The API works great and I am quite pleased with how it turned out.
However due to the way KTA is accessing methods in classes I have used "Data classes" (dont know if that is the right word) to use as input parameters for my methods. To be clear these methods have no functionality other than to store data for methods to use, the reason I am doing this, is because of the way it is structured in the KTA class inspector (I am assuming that KTA uses the IL Code from my library to create a list of classes and methods).
This is what I am expecting the user is shown when they are using my methods. As you can see by using classes as input parameters I get this nice hierarchical structure.
By using classes as input parameters another issue occurs which is that my "Data Classes" are show in the list of classes, which produces alot of unnecessary clutter.
Is there a way to hide these classes from the inspector? I get that it might be an internal KTA issue, which of course would mean I am not asking in the right place, and it is an internal Kofax issue.
However if there is some C# or .NET way of doing this, that would be preferable.
There are a number of different terms for the data/parameter classes that you mention, such as DTO (data transfer objects), POCO (plain old C# objects), or the one that you can see in the KTA product dlls: model classes.
There is not a direct way to hide public classes from KTA. However, when you use the KTA API via the TotalAgility.Sdk.dll, you notice that you don’t see all of the parameter classes mixed in with the list of the classes that hold the SDK functions. The reason is just that these objects are in a separate referenced assembly: Agility.Sdk.Model.dll. When you are configuring a .NET activity/action in KTA, it will only list the classes directly in the assembly that you specify, not referenced assemblies.
If you are using local assembly references in KTA, then this should work because you can just have your referenced assembly in the same folder as your main dll. However if you are ILMerging into a single dll to can add it to the .NET assembly store, then this approach won’t work.
When ILMerged together, the best you can do is to have your parameter classes grouped in a namespace that helps make it clear. What I do is have a main project with just one class that acts as a wrapper for any functions I want to expose. Then use ILMerge with the internalize option, which changes visibility to internal for any types not in the primary assembly. To allow the model classes to still be public, I keep them in a specific namespace and add that namespace to the exclude list for the internalize command. See Internalizing Assemblies with ILMerge for more detail.
Keep in mind that anyone seeing this list is configuring a function call with your dll. Even if they are not a skilled developer, they should at least have some competence for this type of task (hopefully). So even if the list shows a bunch of model classes, it shouldn’t be too hard to follow instructions if you tell them which class is to be used.

C# Xamarin Two types which are the same, not seen as the same

Im getting myself in a muddle so any pointers in the right direction would be greatly received.
I have a Mobile App that im writing using Xamarin Forms.
In the main app I have a 'Connected Service' - which was declared using a WebService WSDL. Its created its own types which is fine.
As the work to connect to the webservice and retrieve data is actually done on the platform dependent project, the same types in the 'parent' project, also exist in the platform dependent projects. For example, the 'parent' has a type/class of 'StationBoardWithDetails1' which has numerous other custom types/classes underneath it.
When the platform dependent project attempts to return 'StationBoardWithDetails1' it comes back as a 'Droid.NameSpace.StationBoardWithDetails1', so when i try to use that in the 'parent' project view model, it complains it doesnt know what a 'Droid.NameSpace.StationBoardWithDetails1' is, but it does know what its own NameSpace.StationBoardWithDetails1 is. I cant seem to convert the two 'StationBoardWithDetails1' across the projects without the compiler complaining.
Error CS0039 Cannot convert type '.Droid.DroidNRE.StationBoardWithDetails1' to '.NRE.StationBoardWithDetails1' via a reference conversion, boxing conversion, unboxing conversion, wrapping conversion, or null type conversion .Android\SoapService.cs Line 95
Any Pointers?
Your Android project can (and should) access the "generated" classes that are in the shared project.
Remove the copy of classes from the Android project.
Declare the generated classes "public".
Where the classes are needed, add a "using" statement referring to the namespace containing the generated classes.
That might be all you need to do. If not, other suggestions follow.
"use .. as a dependency":
Remove any WebService code you put in shared project. Then from shared project, when you need access, you use a DependencyService, to invoke the android code.
Sounds like you need Types that are not in the Droid namespace. Use partial classes.
In shared project:
namespace NRE {
public partial class StationBoardWithDetails
{
// Members that DON'T depend on Android namespaces.
}
}
If these classes need any Android-specific code:
In Android project:
namespace NRE {
public partial class StationBoardWithDetails
{
// Members that DO depend on Android namespaces.
}
}
IMPORTANT: Even though the second code snippet is in your Android project, you still use the shared namespace.
If the above isn't the solution, then add to question enough code to understand how/why Droid.NameSpace.StationBoardWithDetails1 is being generated from the WebService call.
Bottom line is that the goal is to instead generate NRE.StationBoardWithDetails1.

Early Binding of a C# COM library in VBA

Although this is a long question the coding and testing part should be really easy to reproduce.
I have created two separate Class Libraries in C# and I think I am running into a name collision problem caused by existing registry keys from my previous projects and trials.
Here are my two classes:
using System;
using System.Runtime.InteropServices;
namespace Test
{
[InterfaceType(ComInterfaceType.InterfaceIsDual),
Guid("ED5D264B-1D80-4A5D-9C14-8297D90B7037")]
public interface ITest
{
// body
}
[ClassInterface(ClassInterfaceType.None)]
[Guid("8B261B92-8EC5-4CDC-A551-67DEB42137FF")]
[ProgId("Test.TestClass")]
public class TestClass : ITest
{
// body
}
}
and
using System;
using System.Runtime.InteropServices;
using ADODB;
namespace Test
{
[InterfaceType(ComInterfaceType.InterfaceIsDual),
Guid("ED5D264B-1D80-4A5D-9C14-8297D90B7037")]
public interface IConnection
{
// body
}
[ClassInterface(ClassInterfaceType.None)]
[Guid("8B261B92-8EC5-4CDC-A551-67DEB42137FF")]
[ProgId("Test.Connection")]
public class Connection : IConnection
{
// body
}
}
I have Exposed .Net Components to COM like this:
In order to access the assemblies from Excel I have added the ADODB references to the assembly, ticked make assembly COM visible and register for com interop. Also, I've added references to each *.tlb file(2 files for two projects) so I can access them using an early binding and use VBA Intellisense.
I have followed the same procedure on another machine and I can use early binding using the Connection as class.
I am thinking there are some old registry keys I haven't deleted on my original machine which will not allow me to use Connection as the class name in VBE. I've manually scanned my registry and deleted everything I could think of related to my project.
I have also deleted the project entirely and used a 3rd party software to scan registry for missing dlls however that didn't help:/
Removed all previously registered GUIDs and applied new ones each time I created a new Project (just in case)
Created new projects using different namespaces and class names (using ADODB;) I haven't been able to use early binding yet like this Test.Connection therefore I am assuming I have a name collision problem. I am suspecting the name class Connection to be causing it although I am not 100% sure.
The Test.TestClass namespace in VBA:
I can declare and use instances of the TestClass type in two ways using early binding:
Dim x as Test.TestClass
Dim x as TestClass
Now going into VBE Object Explorer F2 the TestClass is properly displayed in comparison to other libraries and general idea of using COMs.
However, when I want to use the Test.Connection library I am unable to use early binding following the same pattern as TestClass because the generated *.tlb file automatically changes(renames) the ProgId's. So, instead I have to bind it like this
Dim x As Test.Test_Connection
Dim x As Test_Connection
and the Object Explorer displays the names using _ (underscores) and not . (dots), which is easy to explain why this happens - keep reading :)
As it stands I am sure it is not the VBE environment that changes the names to avoid collisions. It is the VS' *.tlb generator.
I went to the assembly folder and opened both *.tlb files in Notepad++. I can clearly see that the *.tlb for the Test.Connection library already includes the names with the _s unlike the Test.TestClass which has .s
I have tried to manually edit the *.tlb file but as its a mixed binary file it takes some effect but also causes Excel to stop responding in some weird ways so I have to avoid this method.
I think I have explained well what the problem is and where it comes from. Now my question is: Are there any attributes to use in C# code to tell the *.tlb generator not to override my ProdIds? Are there any alternative ways of manipulating *.tlb files? Is this issue a name collision and is it avoidable without changing the name of Connection class?
I'm sorry for such long question but I have been digging and digging for almost a week now and I still cant solve this.
Note: In VBA ( or VBE Object Explorer ) using IntelliSense ctrl+space it does not seem that either Connection or Recordset have been used. Since they are not already reserved in the VBE environment I recon it has to do with my library itself.
As a reference to why this issue has been raised here, please see VBA equivalent to C# using or VB.NET imports creating aliases
Thank you very much for your time!
Do avoid focusing on the ProgId. You are not actually using it, the dialogs that you made a screenshot of show the actual class names, not the ProgId.
Getting the class name renamed to "Test_Connection" is normal behavior for the type library exporter. It will do so whenever it detects a conflict with another interface or class name that has the same name. You are certainly increasing the likelihood of this happening by also having a dependency on ADODB, it also has a Connection class. A very trivial solution is to simply rename your own type.
Your code snippet cannot reproduce this problem. But of course it is incomplete, we can't see what you are really doing in the code. You'll bring in the dependency on ADODB if any of your public methods use a type from this type library. Also note that there are non-zero odds that this will happen by accident. You might have written a method that intended to use your own Connection type but the compiler resolved it to the ADODB type.
An essential tool to debug this is Oleview.exe, run it from the Visual Studio Command Prompt. First create the type library for your C# assembly with Tlbexp.exe. Then use File + View Typelib, you'll see the content of your type library expressed in the IDL syntax. You'll have little trouble recognizing the mapping of your C# types to the IDL declarations.
Pay attention to the importlib directives at the top of the file. They should look like this:
// TLib : // TLib : mscorlib.dll : {BED7F4EA-1A96-11D2-8F08-00A0C9A6186D}
importlib("mscorlib.tlb");
// TLib : OLE Automation : {00020430-0000-0000-C000-000000000046}
importlib("stdole2.tlb");
There should only be those two. The first one imports the .NET types, defining _Object. The second one imports standard COM types, like IDispatch. If you see additional ones here then you increase the odds of a name collision.
This IDL also gives you a way to solve the problem, in case it is unsolvable, you can edit it to name the types the way you want them. Save it to a .idl file. And compile it with midl.exe /tlb to generate a type library with your preferred names. Do note that this is not something you want to have to do often.

Why doesn't C# have package private?

I'm learning C# and coming from a Java world, I was a little confused to see that C# doesn't have a "package private". Most comments I've seen regarding this amount to "You cannot do it; the language wasn't designed this way". I also saw some workarounds that involve internal and partial along with comments that said these workarounds go against the language's design.
Why was C# designed this way? Also, how would I do something like the following: I have a Product class and a ProductInstance class. The only way I want a ProductInstance to be created is via a factory method in the Product class. In Java, I would put ProductInstance in the same package as Product, but make its constructor package private so that only Product would have access to it. This way, anyone who wants to create a ProductInstance can only do so via the factory method in the Product class. How would I accomplish the same thing in C#?
internal is what you are after. It means the member is accessible by any class in the same assembly. There is nothing wrong with using it for this purpose (Product & ProductInstance), and is one of the things for which it was designed. C# chose not to make namespaces significant -- they are used for organization, not to determine what types can see one another, as in java with package private.
partial is nothing at all like internal or package private. It is simply a way to split the implementation of a class into multiple files, with some extensibility options thrown in for good measure.
Packages don't really exist in the same way as they do in Java. Namespaces are used to organize code and prevent naming clashes, but not for access control. Projects/assemblies can be used for access control, but you can't have nested projects/assemblies like you can with packages.
Use internal to hide one project's members from another.

C#: Partial Classes & Web Services: Separating form and functionality

I am dabbling in the world of web services and I've been making a simple web service which mimics mathematical operations. Firstly it was simple, passing in two integers and then a binary operator would be applied to these (plus, minus etc) depending on the method called.
Then I decided to make things a little more complex and started passing objects around, but then I discovered that a web service only exposes the data side of the class and not the functional side.
I was told that a good way to deal with this is to make the class on the service side a partial class (this side of the class encapsulating form) and on the client side have another partial class (where this side of the class encapsulates functionality). This seems like an elegant way of doing things..
So, I have set up two classes as described above, but it doesn't seem to be working as I was told.
Is what I am attempting possible? If so, where am I going wrong?
Partial classes are really a tool to separate auto-generated code from developer code.
A good example is the windows forms designer in VS, or the new DBML Linq DataContext generated code.
There's also an argument for using them with VSS style source control providers where only one user can edit a file at any one time.
It's not a good idea to use them for logical separation of functionality - the division only exists pre-compilation. As soon as you compile you get just the one class, but not one that it's easy to debug or track operations inside.
What you've described sounds like a really good situation for using WCF contracts. In that case both client and server would share an Interface (or Interfaces).
Your complex code would go there and could be unit tested separately - i.e. outside of your connected application. Then when bugs are found you can eliminate code issues quickly and move to investigating connection related ones instead.
Not with partial classes. A partial class is a syntax construct that gives you the ability to have different parts of the class in different source files. However, all parts of the partial class are ultimately compiled into the same binary.
You could use extension methods to add functionality to your class that represents the data contract.
You could also try implementing the class in a shared assembly and use the svcutil.exe /reference to get it imported in the client proxy instead of having a brand new declaration in the web service namespace.
As Franci said, it simply allows you to put separate parts of the same class into different files.
How you should structure things instead really depends on what you are doing. If I were you I would likely have a rather plain data carrying class and a consumer which could be used to process that data.
The use of a shared assembly is also a good idea. However, if you really wanted to be able to send the code from the server to the client CSharpCodeProvider would work.
(This thread's probably dead but...) I was thinking of doing something similar, but with the functionality on the (in my case) Windows Service.
Both the client program and the Windows service need access to the data, but only the service needs to actually do anything with the data; they are both including in a dll that holds a partial class containing contracted data members, however I get an error saying this partial class conflicts with the partial class on my service even though they are both in the same namespace and at the moment, the server's partial class is empty.

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