I was looking to separate my LINQ to SQL data layer from the rest of my application. So, I decided to move the files to a class library. This way, when my application builds, all of my LINQ files are found in MyApp.DL or something similar. However, I wanted the class library to use the SQL connection that I have set in my web.config. Because the class library does not have a reference to System.Configuration, I had to add that first. I then created a partial class for my Context object. Inside, I created a new constructor with a boolean parameter called UseWebConfigConnectionString. My web.config would contain a generic connection string name called LinqSqlConnectionString. This allows me to make changes to the LINQ files, save them, and not affect this method. So, here’s what I ended up with:

web.config

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<connectionStrings>
    <clear/>
    <add name="LinqSqlConnectionString" connectionString="{insert settings here};" providerName="System.Data.SqlClient"/>
</connectionStrings>

MyApp.DL.ExtendedLinqObjects.vb

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Imports System.Configuration

Partial Public Class MyDataContext
    Public Sub New(ByVal UseWebConfigConnectionString As Boolean)
        MyBase.New(ConfigurationManager.ConnectionStrings("LinqSqlConnectionString").ConnectionString, mappingSource)
        OnCreated()
    End Sub
End Class

sample.aspx.vb

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Dim db As New MyDataContext(True)

This seemed to be the easiest way to pull from my connection strings setting. Although, I’d highly recommend encrypting your connection string before deploying to production.