How to Access a connectionstring from another project

I got two project in my solution in Visual Studio 2010.

Project 1 con开发者_开发技巧tains an app.config with a ConnectionString.

How can I access that ConnectionString from Project 2?

Since they are both using the same ConnectionString, I would prefer to only have one instance in my solution.

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You can add the files as a link to the file to one of your projects.

Use Add an Existing Item to the project you want to add the file to - the Open button has a small down arrow, if you click that you can select Add as Link.

This will add the file as a link from the original location, meaning you only have one physical file.

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Another idea is to use an IoC container, like Ninject, injecting the connection-string into the constructor of the class you need it in. This is not unlike the factory pattern.

Note: you don't need to be using Entity Framework to use Ninject.

See this post: Ninject - binding constructors with arguments / Entity Framework connection string

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Beside of the file linking suggested in the answer by Oded, you may consider refactoring your application to use a commom data access assembly that contains a DatabaseConnectionFactory class or the like. This assembly would contain the connection string in its settings

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If there is only specific section you'd like to share (connectionStrings in your case) then linking wouldn't work for you. Instead you could do something like this:

The solution is to store the connection strings on the web.config of the parent web app. 
Note that the web site root is also an app, so you can store a web.config in there (i.e. c:\inetpub\wwwroot\web.config) which will be inherited by all apps under it.
c:\inetpub\wwwroot\web.config -> common configuration. 
c:\inetpub\wwwroot\app1\web.config -> configuration for app1
c:\inetpub\wwwroot\app2\web.config -> configuration for app2. 

In the case the default web site root is off limits, you can create a root app to contain all other apps and store the common configuration there. 
c:\inetpub\wwwroot\myrootapp\web.config-> common configuration. c:\inetpub\wwwroot\myrootapp\app1\web.config -> configuration for app1 c:\inetpub\wwwroot\myrootapp\app2\web.config -> configuration for app2.

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If your Project 2 has a reference of Project 1 then Project1 may have a class with a ConnectionString property exposed.

By the way, the "class" may read the connection string from the app.config