从dll中的WebConfig文件读取连接字符串

Question

I have a class library project(dll) and an MVC project(I'm using ASP.net Core with .net framework). How can I read the connectionstring that is inside the WebConfig file of my MVC project in the dll ? I'm inside the dll and I need to read it, I don't want to put the connectionstring hardcoded in there too if I have it already inside the WebConfig of the MVC project, how could I do that? I'm using in my dll this code but it's not working:

   var connectionString = ConfigurationManager.ConnectionStrings["MyConnectionStringName"].ConnectionString;

Answer 1

Pass the connection string in as an argument when you use / instantiate your class from the class library rather than attempting to access web.config directly from the class library. This is a fairly common practice and will be more recognizable to other people who may need to maintain your code.

//in the MVC code somewhere
string conStr = null;
if(ConfigurationManager.ConnectionStrings["MyConnectionStringName"] != null)
   conStr = ConfigurationManager.ConnectionStrings["MyConnectionStringName"].ConnectionString;
else
{
   //connection string not found
}
//instantiating class from the class library
var myFoo = new Foo(conStr);