I created 2 dummy projects in my application and named them BAL and DAL. When I build them, they build successfully. If I add a reference to BAL to the DAL project, it added nicely. But while adding the DAL reference to the BAL project, I get the following error:
A reference to DAL could not be added. Adding this project as a reference would cause a circular dependency.
Can anyone help me to solve this error?
Here's what you need to do:
Right click on the DAL Project in the solution explorer and select Project dependencies in the context menu.
You will now see a window that shows the project dependencies of the DAL Project. Make sure that BAL isn't checked.
Now you should be able to add your reference...
I hope this helps I've tried to keep it as simple and straight forward as possible.
Explanation:
Your DAL should not be able to access the BAL. Your code reference dependencies should be like this:
MVC project -> BAL -> DAL
The MVC project should reference the BAL, the BAL should reference the DAL. Set up your project like this. Make it work and then you will better understand why this setup is better.
Given:
Data = raw numbers and strings
Information = processed data into something meaningful
Cosider the following:
The UI should get its information from the BAL which could be able to compose it's data based on the DAL.
You can only reference in one way otherwise you get the error like you said. Just do this: delete the reference from your DAL to your BL and make a new one from your BL to your DAL!
It is implicit in the concept of "layers" that higher layers depend on lower ones, and not the other way round. If 2 "layers" are mutually dependent, then one is not higher than the other, they are not layers in any meaningful sense, and so can be considered to be in the same layer. The same basic principle holds for architectural components or modules, as enforced by Studio for project dependencies. If you use this principle - think of your projects as design modules rather than e.g. just throwing everything into a single project - you will have well-structured codebase which will give you far less problems as it grows in size.
That would cause a circular dependency. What you perhaps want to do instead is have a main application project, which references the BAL, and then BAL referenes DAL.
Data access should not need to reference business logic.
This just happened to me. You have a circular dependency, i.e. two projects both referencing each other. You need to make one of them independent of the other. Takes some time and it happens so quick. One second I was happily coding along, and the next I had 45 errors like this. Just took some time but it makes your architecture/program structure better too, helping you sort out dependencies properly.
Occasionally, you have two different projects, each of which needs methods that the other has. In this case, you can either make a third project and move the shared code into there, or choose one of the two projects to put the shared code in.
This problem occurred to me when I was building a WPF application with several layers like repository interface layer, repository service layer, sql service layer, rest service layer and my main WPF UI layer.
I resolved this error. I noticed that some of the layers were
unnecessarily referencing other projects. I removed this unnecessary
reference.
Then I noticed that some of my service layer and repository layer
had my WPF UI project as reference(My StartUp project); this is
what was creating circular reference. I removed this.
========================================================================
Conclusion: Check each projects reference dependency and make sure there are no unnecessary reference. Make sure sub layers are not referencing the startup project in the reference.
Hope I was helpful.
In my case I copied a project file without generating a new ProjectGuid. Since Visual Studio uniquely identifies projects using the ProjectGuid, it assumed the project was trying to reference itself.
in my case the project was somehow already declared in refrences in csproj.cs in the targeted project so simply i removed all the dependency in csproj.cs and tried to add from main project again and it worked
I had two projects called Application and Persistance that the reference of the Application project to the Persistance project encountered a circular dependency error.
By clicking on the Application project and looking at the values used inside it, you will notice that the Persistance project is include inside the <ItemGroup> tag, which is why you receive a Circular Dependency error.
To fix this error, just Comment this Include.
To get around this, add the reference by browsing to the projects DLL after it has been built. Do not select it from the "Projects" tab.
Related
Actually, question was set in the Theme of the message. But yet again,
i have Solution with 3 projects, two of whitch are Static libraries and one is Application. How my Application project could know from where to pull these .libs.
Yeh, i can do it from Linker->Input->Additional libraries, but i think there are must be other way if projects are in one solution.
There is another way, works on VS2010 and up. Right-click your EXE project, Properties, Common Properties, Framework and References. Click the Add New Reference button and select your project that generates the .lib. Repeat as necessary.
This does two things, it takes care of the Additional Dependencies linker setting, automatically adding the output of the library project. And it ensures that projects are built in the right order, normally something you'd have to with the Project Dependencies command. In your given example, with enough machine horsepower, the library projects will build concurrently. And the main project won't start building until they are both done.
There have been many posts on this topic, but I have yet to find the "real" solution.
How does one manage their dependency tree (both compile time and runtime) using MSBuild project files (i.e. Visual Studio project files via project and file references)?
It is well known that project references from child projects will not be copied to an application bin directory if there is no compile time reference, even if there is a runtime dependency, and even if copy-local=true. Hence, any loosely coupled component will not be copied over.
The hack to solve this problem is to include the dependency in the parent project with copy-local=true. However, this basically destroys your dependency tree as you no longer know where the dependency is and ultimately, as your app grows and morphs, you end up with a version of DLL hell. Your parent project ends up with 10s to 100s of dlls, most of which are runtime dependencies of dlls in child projects.
Another hack is to write a custom targets file and call it from every project file: http://blog.alexyakunin.com/2009/09/making-msbuild-visual-studio-to.html. But surely there is a better option. This is such a bread and butter thing. Java devs never have to deal with such trivial issues.
From what I can gather, the Microsoft way to solve this problem is to register every dependency in the GAC for every dev, test and production machine. But this is stupid and annoying. I won't bother giving this option and educated rebuttal.
Avoiding the GAC option, how could one use MSBuild to manage a dependency tree that includes runtime only dependencies? How does Microsoft do it? Surely they don't run custom targets files like the one in the link above.
I hope someone from an enterprise .NET background can step up and offer some real advice on this. Otherwise I'm just going to have to rewrite all my build scripts in NAnt (shudder).
Thanks All.
UPDATE
In response to some comments, the following is a practical example of the issue from my current project.
The app is a Web Application project that exposes a suite of WCF services. It has an external domain DLL containing the external service classes and an internal domain DLL containing internal service POCOs, domain objects and DAOs. There is a separate integration DLL containing interfaces (DTOs) for all the internal domain classes that allows us to completely decouple the external and internal domains. The whole thing is wired up with Spring.net. I hope this is clear, let me know if you need more clarification.
My current build process is to use MSBuild to generate a deployment package for the web application (in TFS Build). So while the whole solution is built initially, only the output from the web application gets packaged. Therefore, the Web Application is treated as the dependency root and I expect that any loosely coupled child references should get copied over on build if they are set to 'copy-always=true'.
So the Web Application contains a reference to the external domain DLL which contains a reference to the internal domain DLL which contains many references to 3rd party libraries and various indirect and loosely coupled dependencies required by the 3rd party libraries.
The problem occurs when there is a 3rd party dependency in the internal domain DLL e.g. oracle.dataaccess which is required by NHibernate at runtime. Even when I set 'copy-always=true' on these DLLs, they do not get copied to the Web App package. The only way I can include them in the package is to add these DLLs to the Web App's references. I don't want to do this because I no longer have a meaningful dependency tree.
I hope this makes the issue clearer. Please let me know if anything is unclear. It's hard to describe this sort of stuff.
If anyone is also having a similar issue, please speak up and share your experience.
I really want to give you a better answer but unfortunately you didn't put enough information about your solution/projects and your dependencies, so I will try to give you several ideas and I hope one of them works.
The easiest thing to do as you said is to set up a separate folder with all of your dependencies and create target file that will copy them to your bin folder. If you have dependencies that are not changing frequently that might work. If another team from your company is building them and they change frequently, this approach is not good.
Another simple approach - if you're referencing your dependencies from your solution only you can change the build path, so that they build directly into the bin folder of your main project. This way you don't have to reference them directly.
Use NuGet. You have a separate team producing loosely coupled dependencies it may make a sense to set up local NuGet repository and use it for that http://juristr.com/blog/2012/04/using-nuget-to-distribute-our-company/
I hope that helps.
On my current project we are using Nuget to bring in dependencies on things like NHibernate, we use Ninject as our IoC container (although that's not an important detail of the problem I'm trying to solve) and we use Ninject's scanning functionality for establishing our bindings.
This all works fine but the problem that I'm facing is that I've gone through the trouble of making my Data Access Layer be exposed to the Application Layer in a Presistence Ignorant fashion but Ninject needs to have access to the NHibernate Dlls at scan time. If I wasn't using Nuget to pull in dependencies then this could easily be solved with a post build step to copy the dependencies from wherever I had decided to put them in my source tree.
However, with using Nuget my understanding is that the path to Dlls could change in the package directory as dependencies are upgraded. I definitely don't want to solve this problem by using Nuget in my Coposite Root projects (services, UX, etc...) and so I'm trying to figure out a clean way to get the dlls that I need at scanning time available in my Composite Root projects execution directories.
I have a project called 'talktome', with no runtime dependencies.
Also I have project 'talktome-tools', which depends on 'talktome'.
No problems, until I realize that the unit-tests in 'talktome' depends on 'talktome-tools'.
What solutions are there?
If talktome is a general project where other (e.g talktome-tools) depends on, it should not be depend on the more specific projects. Then, it would be wise to get rid of dependency from talktome to talktome-tools.
Otherwise, you would create a more higher level project (e.g parent) and put necessary interfaces, classes that can be used by both talktome and talktome-tools to the new project.
You may move the tests to another maven module like talktome-tests that will do the integration testing. It makes sense especially it seems that talktome shouldn't depend on specific project like talktome-tools.
And, test dependencies like talktome-tools should be included with test scope.
I have an msbuild project which builds a SLN file from visual studio which holds all the projects in (about 70+ project), and a lot of the projects are dependent on each other meaning they need to be build in order - sometimes a developer forgets to set the build order manually in visual studio in the solution file causing the msbuild on a clean solution to fail as something gets built out of order/cant find a dll.
Is there a way for msbuild to take all projects and work out the dependencies and build the projects in order, if there is how do i do this? using an MSBuild task? With current tries it seems to just build in the order it reads the projects in - if i pass in a list of project files+paths.
Currently the only way i can think to solve this is a external app which scans the proj files and references and then manually creates a solution each time.. but this seems overkill for such a simple thing.
Anyone solved / seen this before?
How are you calling MSBuild? If you point MSBuild to the solution file, it should be able to work out the dependencies. If you point it to individual project files, then it won't be able to resolve any project references.
If you don't use project references you can still control the dependency order in a solution by using the "Project Dependencies" dialog to manually set the dependencies.
While Project Dependencies are hard to maintain and not shared across .sln files, Project References are honoured and do dictate the order consistently - see the ResolveReferences task in Microsoft.Common.targets.
ASIDE: A 'friend of mine' may 'during a refactoring' have accidentally stubbed out their Build Task and it's DependsOnTargets linkage to the Microsoft.Common.targets ResolveReferences task and ended up with ProjectReferences not being honoured in ways that sound like the question here. If you read some of the posts, you might get the idea that it's all mad shaky - it's not; the shaky bits are the Project dependencies, not the Project references.
See this excellent MSDN Blog article by Dan Moseley that really explains the topic, including some useful workaround strategies. (via this mildly related issue with building xUnit.net).
If all of your dependent projects are in the solution and you are using Project references, Visual Studio should manage the dependencies for your and build in order of that dependency list.
It sounds like you are not using project references. I always recommend project references.
This is an old question but the issue was most likely that projects in the solution used direct references to dependent DLLs (Add Reference > select Browse tab > select dependent DLL) instead of using project references (Add Reference > select Projects tab > select dependent project). With direct references, Visual Studio can't figure out the dependency chain. You must tell it by right clicking on the solution node and select Properties. Pick Common Properties > Project Dependencies to set the required projects. Mr. Klaus is correct but I wanted to document how to fix this issue.
While it is correct that MSBuild should observe the build order when you use project dependencies there is one caveat. It doesn't at present observe the reverse build order when building the clean target (as I have blogged about here). For regular build however it works nicely as described by others here.
I am using Msbuild 4 found at c:\Windows\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe
It seems to solve the problem.
There is no Microsoft tool that will examine all the dependencies of your 70+ projects and generate a solution file with dependencies clearly declared for you.
You have to do that on your own by using 2 different methods:
Manually specify a dependency, for the solution, in visual studio.
Specify a project reference in the project file itself.
If you don't want to do that, then you will have to swallow the medicine and accept that you will to use an external tool to do that for you. Yes it's clunky but it can be made to work. If you check in your solution file to your source control you can mitigate these problems. As long as you have an active solution file to work with.
I at one point didn't, and I had 600+ projects in the build. So I wrote a tool (years ago) that would automate 99% of this work. It uses the .NET MSBuild API's to read the msbuild files (no recreating the wheel here with xml api's). It then examines outputs and inputs and generate a dependency tree which I can then do a few things with it:
Spit out a solution file.
Do a dependency sort (also a topological sort in academia), and spit out those projects in order they should be built (for a non-parallel type of build, which can be useful sometimes).
print out all sorts of diagnostic information about dependencies.
The only limitation I have seen with the tool is with a few crazy COM dependencies which are pretty sketchy anyways. Which I added a super simple work-around.