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Apologies for the shouting but this is important.
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Insults, slap-downs and sarcasm aren't welcome. Let's work to help developers, not make them feel stupid..
cheers,
Chris Maunder
The Code Project Co-founder
Microsoft C++ MVP
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cheers,
Chris Maunder
The Code Project Co-founder
Microsoft C++ MVP
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Hello,
I have a VS project to implement a dll.
This dll is a kind of "Master" dll and it should be possible to extend its functionality with "Extension" dlls without touching the "Master" dll.
The "Master" dll should check everytime when it is loaded, what other dlls are available and thus extend or reduce its functionality by itself.
If "Extension" dlls are missing, the "Master" dll should recognize this without any error and function with reduced functionality.
Any hints from your side which approach would make sense here.
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That sounds the wrong way round to me. The base (not master) dll should not have, or even need, any knowledge of extensions. The point of an extension class is to offer extra or enhanced functionality to an application. So the only process that needs to know whether the extensions are present is the application that wants to use its features.
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The "Master" dll (or base dll) is the application in this case. It is a plugin dll for a software where i do not have the source cose and also extends the functionality of that software. So you could consider the base dll as the application.
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That is not something I have ever had to work on.
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Hi,
I have an appliction that loads extensions from a specific folder; each extension is a class that derives from a base class DTF_ComponentBase, which happens to be a UserControl as all extensions need a very similar dialog window. Each extension is built into a separate DLL file. This is the heart of the code that loads those DLL files:
private readonly List<DTF_ComponentBase> DTFlist=new List<DTF_ComponentBase>();
...
DTFlist.Clear();
string folder = Path.GetDirectoryName(Process.GetCurrentProcess().MainModule.FileName);
log("folder=" + folder);
Directory.CreateDirectory(folder);
string[] dlls = Directory.GetFiles(folder, "*.dll");
Exception firstException = null;
List<string> errors = new List<string>();
foreach (string dll in dlls) {
if (dll.Contains("LPplatformDLL.dll")) continue;
try {
log("File: " + dll);
if (dll.Contains("DTF_ComponentBase.dll")) continue;
Assembly asm2 = Assembly.LoadFile(dll);
Type[] types = asm2.GetTypes();
foreach (Type type in types) {
if (type.IsSubclassOf(typeof(UserControl))) {
UserControl uc = (UserControl)Activator.CreateInstance(type);
if (uc is DTF_ComponentBase comp && !comp.Skip) {
DTFlist.Add(comp);
break;
}
}
}
} catch (Exception exc) {
if (firstException == null) firstException = exc;
errors.Add("Error loading "+dll+"; "+exc.Message);
}
}
At the end DTFlist contains all the extensions that were found and instantiated; a foreach loop can then be used to issue commands such as Start, Stop, ... whatever the base class provides.
Hope this helps.
Luc Pattyn [My Articles]
The Windows 11 taskbar is a disgrace; a third-party add-on is needed to reverse the deterioration. I decline such a downgrade.
modified 24hrs ago.
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Presumably you have a well designed understanding of what the additional functionality is in general.
There are a number of design patterns that might be useful in structuring the code.
- Chain of responsibility
- Fly weight
- Decorator
- Composite
- Template
As suggested other response you use reflection to load classes dynamically. Those will need either an interface or base class for your code to interact with it. You will need to at least consider dependencies (other dlls required by the dll that is loaded) in that they must be located somewhere. Either load those also dynamically or insure that the application can find them.
AtaChris wrote: with reduced functionality
That is a design and business consideration which cannot be addressed generically. For example perhaps you want to switch out your database driver. But the application cannot operate without any database. Same thing with supporting multiple card card processor interfaces. If you expect two but only find one then that is ok. But if you find none then the application probably cannot continue.
There are ways around failure cases but they add significant complexity and even business risk.
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I'm having trouble getting my mind around how a default method in an interface works.
Picture the below interface and default method implementation:
public interface IClientForm
{
delegate void WindowClosedDelegate(object sender, WindowEventArgs args);
event WindowClosedDelegate OnClosed;
long FormId { get; set; }
UIContextClass UIContext { get; set; }
IClientForm ParentForm { get; set; }
void Window_Closed(object sender, WindowEventArgs args);
}
public static class IClientFormHelper
{
public static void SetUiContext(this IClientForm iClientForm, UIContextClass _UiContext)
{
iClientForm.UIContext = _UiContext;
iClientForm.FormId = _UiContext.AppContext.ClientGetUniqueFormId();
iClientForm.UIContext.AddForm(iClientForm);
iClientForm.OnClosed += iClientForm.UIContext.Window_Closed;
}
}The main problem I see right now is that the default method code never runs. I assume the code is supposed to run as soon as I call the setter for UIContext that's declared in the main interface.
Apparently, this is something I don't understand.
What I want is for every IClientForm window to run the default code whenever the UIContext setter is called for that form, so that each separate window class doesn't need the same code repeated inside of it.
Can someone spot what I've done wrong and point me in the right direction? I sincerely appreciate your time.
The difficult we do right away...
...the impossible takes slightly longer.
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Thanks Luc. If you say it's complex, then it must be too far for me to grasp. 
I've decided to use the IClientFormHelper class as an extension method call, that I will just have to repeat in my IClientForm window classes.
The difficult we do right away...
...the impossible takes slightly longer.
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Hm. The one link shows there are many aspects to the default implementation inside interfaces, that article is hard to read and understand in one go.
The first answer in the SO link shows how a default property getter could be written; that is simple, and at first glance what you want could be implemented likewise as a default setter.
Luc Pattyn [My Articles]
The Windows 11 taskbar is a disgrace; a third-party add-on is needed to reverse the deterioration. I decline such a downgrade.
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That's one of the major things that stumped me. Since an interface can't contain data members, then if I try to write a default setter, I have nothing to assign it to.
It was at that point that I gave up!
EDIT:
Maybe I should solve the problem by using the inheritance of a base class, rather than trying to stuff it into the interface.
That gives me an idea...
The difficult we do right away...
...the impossible takes slightly longer.
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You could use properties rather than variables, couldn't you? That is what the example does...
Luc Pattyn [My Articles]
The Windows 11 taskbar is a disgrace; a third-party add-on is needed to reverse the deterioration. I decline such a downgrade.
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Yes I could use properties, but at some point in the call stack, the value must be assigned to a data member in the window instance.
So that's code that must be repeated in each class, unless I derive from a base class.
The difficult we do right away...
...the impossible takes slightly longer.
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Richard Andrew x64 wrote: default method in an interface works.
Default interface methods - C# feature specifications | Microsoft Learn[^]
"to add methods to an interface in future versions without breaking source or binary compatibility with existing implementations of that interface."
The feature is a hack which should be avoided if possible.
It does not fit your case. An abstract class is a better starting point for your example.
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Console.WriteLine doesn't write to the debugger Output window in .NET 8.
It always works in the .NET Framework, but not in the new .NET.
The difficult we do right away...
...the impossible takes slightly longer.
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Ah! Makes sense. Thanks!
The difficult we do right away...
...the impossible takes slightly longer.
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Hi
I need to make a game using window form in c#
just an example
thx.
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While we are more than willing to help those that are stuck, that doesn't mean that we are here to do it all for you! We can't do all the work, you are either getting paid for this, or it's part of your grades and it wouldn't be at all fair for us to do it all for you.
So we need you to do the work, and we will help you when you get stuck. That doesn't mean we will give you a step by step solution you can hand in!
Start by explaining where you are at the moment, and what the next step in the process is. Then tell us what you have tried to get that next step working, and what happened when you did.
Just saying "I wanna write a game" doesn't help anyone!
If you are having problems getting started at all, then this may help: How to Write Code to Solve a Problem, A Beginner's Guide[^]
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!
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How do I check for existance or clear the contents of a SharePoint List from C# code?
I have complete the code that creates a sharepoint List from scratch, creates the columns, and loads the data that I get from an API GET query of an external database.
How do I:
check and see if the SharePoint List already exists
clear the contents of the sharepoint list
load the list with new data.
Without doing these steps, I am left with creating the list from scratch each time and giving it a unique name each time.
Is there some source of information on how to do this that I can find online? The Microsoft AI chat bot has given me some code that does not work at all.
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