I’m writing an application using Entity Framework and ASP.NET MVC, so I decided to separate DAL from MVC Web Application. And actually everything fine except next problem (if it’s problem): I had to copy Entity connection string from app.config of DAL project to Web.config of Web Application. And actually it’s look correct: DAL should not to know about connection string to Data, it’s duty of Main Application.
But I really don’t like, that I have to keep Entity connection string in app.config of DAL, because it’s need to update my EntityModel (*.edmx). Is there some best practice to reference to connection string of Web Application? Or shoul I just leave it like it is now?
So, just an an explanation of what is occurring here. When you are developing your application, the DAL project is, by nature, it’s own project. When editing the DAL project, Visual Studio will use the values in the projects configuration file. Thus, why the connection string staying in that app.config file.
Now, when you publish your entire solution to a web server, the web application is the actual application that is running. This has a reference to the DAL dll that was complied during the build process. Given this, the DAL dll will get all of its configuration values from the web.config as this is the configuration file for the primary executing assembly.
To answer your question, its probably best to keep them in both the app.config and web.config for no other reason than you will not have to ‘create a new connection’ each time you need to update your model. The DAL project, as far as I know, will not ever look to another projects configuration file while in Visual Studio. However, having connection strings in both the app.config and web.conig will not impact your deployment. The web.config settings will always be used.