添加项目参考与添加 DLL 参考

Question

I am newbie in .net.Today I have created a sample. In that sample, I have stored data in database using N Tier architecture. If I want to use to Use BL or DAL method in other project(I mean BL method in UI or DAL method in BL), I found two ways.

First one is - Right click on project << Add Reference << Select Project in Project tab

Second one is - Right click on project << Add Reference << Select DLL in Browse tab

Could anyone tell me that is there any difference between both of them as both works same.Is DLL way better then Project Reference.If yes, then what is the benefits?

Thanks in advance.

Regards, Mohit Kumar.

Answer 1

The correct way to do it is to add a project reference.
one of the most important differences is that a project reference is updated automatically when you change the referenced project.
for example- If you change your DAL method from GetEmployees() to GetAllEmployees() then you can use GetAllEmployees() immediately in your BL class, without compiling your DAL first.

Answer 2

You typically use the project reference when the reference is part of your solution. In this way the relevant latest code is always used.

You will reference an assembly when it is a third party component or not part of your solution. This is somewhat more static as you will be using the code at the version represented by the assembly. So any changes to the assembly will require you to physically overwrite the referenced assembly with the updated dll.

HTH

Answer 3

I have came across a very interesting difference between the two approaches, but in the context of having 2 projects, one shared among multiple developers and one private to each developer.

Let us say that the shared VS project is called projectS, and the private project is called projectP

Now if the objective is to have a centralized development, and the developer needs to access source definitions from both projectP and projectS so that pressing "F12" or "Go To Definition" in VS would bring complete definition, then we have to use the Project Reference and not the DLL reference, otherwise pressing F12 would bring the definition from the compiled "metadata" excluding all developer comments and other relevant data.

When adding a Project Reference to projectS from within projectP, VS will resolve references to the files included in projectS and referred to from projectP using the source definition in projectS, and not from "metadata" of the DLL associated with the referenced project (ProjectS.dll). Still, the projectS.dll will be included in the References folder and Development time, Execution time will be OK.

When adding a DLL reference, VS will resolve references from "metadata" stored in ProjectS.dll, even if the Referenced Project was added to the Solution of projectP as an "Existing Project". This would allow Execution time to be OK, however, Developer will not be able to press F12 and go to Source definition in projectS, he/she will have to do this manually from the solution search area.

Answer 4

The differences between the 2 have already been answered, however just to add to that, I think the only difference between the 2 in VS is that if you add project reference it still adds a normal dll reference, except the reference is to the Debug location of the projects binaries (ie bin\debug\project.dll), so in essence you could probably just Add Reference in the same way and point straight to the latest compiled dll.