LINQ to SQL connectionstring

You can pass an override connection string into the DataContext constructor:

var db = new MyDataContext("Data Source=Something Else;")

I think that the best way to do it is a combination of Albin's and Rup's answers. Have a value in the config file, and then read it at run time and feed it to the context constructor, something like this:

WEB.CONFIG:

<appSettings>
<add key="ConString" Value="The connection string" />

CODE:

//read value from config
var DBConnString = System.Configuration.ConfigurationManager.AppSettings("ConString");

//open connection
var dataContext= new MyDataContext(sDBConnString)

this way you can change the connection string even at runtime and it will work and change on the running program.

The DBML class (YourDataContext) has an overloaded constructor which takes ConnectionString, so try instantiating that instead of the default one.Get the connection string from app.config and use that to create the instance.

YourDataContext context = new  YourDataContext (ConfigurationManager.ConnectionStrings["ConnStringInAppConfig"].ConnectionString)