I'm working on a Windows forms application that shows a list of PDFs in a given folder, with a toolbar with buttons that carry out operations on the list of PDFs. The form has a data grid view that takes as its data source a list (PDFlist) of objects (PDFentry) that have properties file name, file date, file size, etc. (Like Windows Explorer).
Because the operations are carried out on the entire list of PDFs, the code for the various operations necessarily loops through PDFlist, acting on each item. That's a lot of code, so form.cs is pretty big (900+ lines). It seemed to me that PDFlist could be its own class, inheriting from List and adding methods for the various operations. Then form.cs would just have a line that said PDFlist.Compress(), or PDFlist.Print(), or whatever the operation was.
But then the red flag was that there's only ever one instance of PDFlist. It's not a singleton in the sense that I don't have to prevent a second instance from being created. It's just that the application only uses one PDFlist throughout.
Would this be a case where a static class is appropriate?
One thing I have painfully learned is that while a static may work now, at some point you will end up using it from multiple threads and then all hell will break loose. If the class has any state, try not to make is global or thread static.
Also, these types of errors are some of the worse to debug.
"Time flies like an arrow. Fruit flies like a banana."
Our company is currently running .NET version 4.5 and using VB as the back-sript language. All of our forms are basically using the general ASP.NET forms methods. In other words we are not taking advantage of the any of the MVC core methods.
We are getting ready to start our new design process and wanted to get some recommendations on what framework and mythologies/C# version/database methods/Web UI methods, to use in our new design.
What skills does your team have / how much new learning are they able to do?
Are you intending to run the old stuff concurrently with the new stuff or is it a big bang approach?
What is the problem domain? That will dictate what are the best tools for the job
Are you willing to risk leading edge (which may be buggy) or do you want trailing edge (which may cause upgrade issues in the future) or do you want to play it safe (e.g. go with the next-to-latest version)?
Who are your clients / customers? What will they be most comfortable using?
Are there off-the-shelf packages that can do what you want which could save you a lot of development time?
Stevey T wrote:
recommendations on what framework and mythologies/C# version/database methods/Web UI methods, to use
In my company we had a system on .net framework platform. That was made from an orchestator, different rest API services on top of a monolithic oracle DB. With a huge plsql library.
We used distributed transaction for the operation (import of data). Because of the rollback possibilities if one request did fail e.t.c. And used a orchestrator in front of the rest API services (micro services) that organized the different requests all in one transaction.
We had to upgrade the system to .net core.
But .net core don't support DTC anymore !
Have anyone had a similar situation, and what what did you do about it?
Or do anyone have any comments to this issue/problem.? That if one request fails in a
big operation of many requests the database data will not be consistent, if no rollback is done.
When we use many "micro"services on top of one monolithic database.
We are thinking of building an internal Kaggle like platform to run Hackathons in our company. I am wondering what would be the best technologies to use for this and how to go about building such a site. Any help appreciated. Thanks.
I have always had the view that duplication is bad. There are always exceptions, but most of the time I it seems bad to me. Unit tests are one are where I tolerate it more but in production code it's something that I rarely find desirable.
Some people duplicate things two or three times and only eliminate the duplication on the third or fourth time. I really can't understand why somebody would blindly follow this rule. I understand the argument that we may not know how to refactor something if there are aren't enough instances of the duplication but I find that it is rarely the case. At least if you don't know how best to refactor something then keep it simple. The rule seems crazy as why would you do something if you know it's bad? Eliminating duplication is usually quick and, in my opinion, usually makes things much easier to read, particularly when you have half as much code to read/understand.
As an example, imagine we want to format a number as a currency. We could have the following
Having it once seems fine, but not really more than once. Surely, as a very simple refactor, something like the following would be better?
Surely the time saved by the readability would outweigh the code of writing it and it solves the problems of duplication.
Deliberately duplicating code doesn't make much sense to me, but maybe I've been working with people who have taken things a bit too far?
The principle of Do not Repeat Yourself (DRY) is one of those areas that is taken too far by some code zealots. Let's take your ToString example here, you notice after a couple of times that you have the same ToString code so you decide to introduce an AsCurrency method. That seems straightforward enough, but you're working in a large codebase so you don't notice that the same logic has been added in pieces of the code that you don't visit. Worse still, somebody has done this elsewhere:
Then there was that piece of code which looks like this.<pre>public class FormatConstants
publicconststring GBP = "£0.##"l
// .... other patterns removed for brevity
What we're seeing here is that others have attempted to avoid repeating code with varying degrees of success. In all of these cases, there is an element of repeated code because differnt people have taken different approaches to to avoid repeating code. Even if the code doesn't look exactly the same, you are repeating the intent of the code. Now you have introduced yet another way to represent this same conversion. In six months time, someone else comes along and has to add a currency ToString in a few places so they refactor their code to avoid adding repeated code. If you're lucky, they have looked through the codebase looking for other places that does the conversion and picks an already written one; if they've searched using ToString("£0.##") then they might not have found the match so they end up adding yet another new way of formatting this one item. What has happened here is that the search to remove duplication has ended up creating a mess - and this is just with a simple example.
The bottom line is, DRY is a great principle and one that you should try to stick to if it makes sense but you have to accept that, in some cases, you aren't going to achieve it and you shouldn't beat yourself up over it.
I decided to start to learn web programming and as a first serious project I want to build a stocks/cryptography portfolio, where user sign in and add their holdings of specific stocks/coins. Users can see the current evaluation of their portfolio, or inspect various types of charts. I would like to host my app in the cloud, so that everyone on the internet can access it. Such sites(with lots of other features) are coinmarketcap.com or coingecko.com .
I have no idea what technologies to use, I know there are plenty of options, so that makes it very difficult for me to make a choice. I would like to use modern but popular technologies, which ideally are relatively easy to learn. I googled for an hour or so, and these technologies were mentioned:
- Google Cloud Platform: Google Cloud Run, Firebase (+ Firebase Realtime Database, Firebase Realtime
Database, Firebase authentication)
- All kind of products from AWS
- Docker, Kubernetes
- Angular, React
- NodeJS, Express
- Python(for backend)
I'd prefer Google Cloud products over their AWS alternatives. I have some experience with Angular, Docker, Kubernetes, NodeJS + Express, and Python. I have no experience with GCP or AWS, but I think I'd enjoy learning them.
So, what technologies (from the ones above, or others), would you recommend for my basic project ? The project basically needs cloud hosting, user authentication and database storage.
Without getting into architectures, you do know you don't need "cloud hosting" in order for people to visit your site? "I would like to host my app in the cloud, so that everyone on the internet can access it."
Cloud hosting of course has advantages (scalability, resilience, potentially performance etc) BUT if you're new to web development, is a large learning curve in its own right. I've been doing web development for 20+ years but both Azure and AWS are so complex to configure, and so unpredictable in terms of pricing (and potentially very very expensive) that to date I've steered clear.
Unless you expect mega take-up of your app, all you need is a basic shared hosting plan with a MySql or SqlServer database, at a cost of under $5 / month in total. It will be much easier to configure and manage, and allow you to concentrate on your application.
Your tech lists above are comparing apples and televisions (not even apples and oranges). Generally, the languages you build your app in are unrelated to the platforms you host on (with some limitations).
TL/DR: What kind of design patterns are useful for the following project:
Frontend: Web/Mobile, simple Word finding game (4x4 board with 16 letters, connect letters to make words)
Backend + database: Check if word exist/ Save scores for highscore/ Save generated boards/ Users/ etc. (I'm planning to use Repository and Unit of Work for Database, and Singleton for settings, userId, etc.)
I'm currently working on the last assignments of my study, and have hit a mental wall for quite some time
One of the assignments is for a class called Design Patterns, where we have to make a drawing program with specific design patterns or use design patterns in a project of our own.
After failing multiple times trying to build the standard assignment, I'm thinking of combining my last two assignments into one, and creating a web-app/mobile-app with backend and database.
Frontend would have a 4x4 board of buttons, with letters on it. The buttons can be tapped and a word can be added.
The backend would check if the word exists, if the word is playable on the
Database will keep highscores, userinfo, earlier generated boards, etc.
I don't know a lot about design patterns, so I was hoping some people with experience could help me with some useful design patterns that I could use. The ones I do know I could use are Repository and Unit of Work for the Database, and Singleton for saving settings and UserId on the mobile app.
When it comes to web applications, the common UI patterns to apply are some combination of Model View Controller, Model View, ViewModel or Model View Presenter. If I were you, I'd look at what you can do with those. If you have experience with more complicated applications then another common pattern to apply is the use of Observables.
Normally I would advise against designing a system just to use patterns but if your assignment is to use patterns then that's what you are going to have to do.