i never use Dependency Injection in apps. i go through few article with Dependency Injection and found the concept is interesting but believe hard to implement in real life. now i want to implement Dependency Injection in my win form apps.
our company work with many shipping company like UPS, Fedex, Purolator etc for now but in future they have plan to works with many other shipping company. i have developed separate separate class library projects for all those shipping company like UPS, Fedex, Purolator and include those dll into our main form apps. the problem is many time we hard code few things in our code like country code etc.
for example i have one form where 4 buttons are there. like those buttons are "Ship with UPS WorldShip", another button there called "Ship with UPS WebAPI", another button there called "Ship with FedEX Desktop Apps" and another last button called "Ship with Fedex WebAPI".
when user click on UPS WorldShip button then a flat file generate in a folder. when user click on UPS WebAPI button then a request goes to UPS site.
when user click on FedEX WinApps button then a flat file generate in a folder. when user click on FedEX WebAPI button then a request goes to FedEx site.
so what i do now when user click on any button then i call a specific function exist in dll to complete the task.
everything is working fine at my end but the problem is when our company start working with another new shipping company then i have to create another class library for that company.
i said i never use DI ever in my apps and have no experience. so some one guide me how could i handle my situation with DI as a result when a new shipping company will join then i do not have to write any extra code. so guide me how to implement DI in my apps and also guide me with how to handle my situation with sample DI code for guidance.
DI doesn't work this way. If you have new functionality, then you have to write code. So, if you add a new company and that has specific logic, then you will have to write that logic - DI is not a magic bullet. What it would do, is save you having to write any logic to hook it up to your UI, for instance.
If you're going to do this, then I'd suggest that you read a few artioles here on Code Project. This[^] is a good place to start. Beyond that, I'd also consider investigating MEF.
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
Adding a bit more emphasis to the previous reply - because you are accessing an external service provider you will always need to write new code for each.
Given your description of how you are implementing this it also seems unlikely that you can generalize it either. Which isn't to say that you are doing it wrong but rather because you are using all the shipping options rather than attempting to normalize it that you won't be able to generalize it. And actually I suspect that if you try to generalize it too much that you could end up with problems.
Tridip Bhattacharjee wrote:
then i have to create another class library for that company.
This doesn't sound like a job for plain DI. It sounds more like a job for MEF which is more of a plug-in architecture.
How much of the code is straight up copy & paste between different companies?
If the code is 99% duplicate, why not just move the differences into a SQL database or XML file and just have a single common engine that reads the params and uses them? I.e. like instead of hardcoding one dll to fedex and another to ups, just have one method where you pass in the URL or whatever?
Even if the code is more like 50% to 75% different, I'd refactor it to a data driven engine instead of a plug-in architecture.
I'm guessing most of the code is identical... go to this URL to create an order, go to this URL to do this, etc.