why use a dll instead of a class

i joined a new project where they use c#. I noticed that several dll's were being add in the references

From my knowledge and the e-learning that i have done, after building a class(which has some Methods & data), a DLL is generated.

Now in a new project, the class that just got converted into a DLL is added as a reference so that the functions defined in it could be called.

So, now my question is: 1) what is the need for converting the class file into a DLL file. Even it were a Class file, I could still be calling the functions defined in it by adding its namespace at the top of the code

2) If After adding the reference of the DLL , I deleted the entire contents of the project, leaving only the dll untouched(and in the same place), would the class using this dll still work

Jon Skeet
people
quotationmark

Separating your code into different projects (each of which will create a separate assembly) has various benefits:

  • It makes the structure of your code clear. For example, it can separate your storage layer from your business logic, and also from your user interface.
  • It allows reuse: two different user interfaces can refer to the same assembly containing the business logic, for example.
  • It allows greater encapsulation: classes which are only needed within their own assemblies can be declared as internal (which is the default for top-level classes in C# anyway) which means code in other assemblies won't even know about them. If all your code is in a single assembly, all those classes will "know about" each other.

Now choosing just how many projects to have is a balancing act - I've certainly seen applications where this has gone much too far, with lots of assemblies containing just a single class. If you have a large number of assemblies, that becomes a headache in terms of project and reference management. However, having too few assemblies makes it harder to reuse that code cleanly.

people

See more on this question at Stackoverflow