LINQ to SQL class library . SharePoint 2013 visual web part

I am doing some tests in using LINQ to SQL class in Visual web part.

I am unsuccessful due to some unknown steps missed and confusion on authentication.

Environment Scenario:

Northwind database with a SQL service account.

SQL server enabled with windows and SQL authentication.

Development Method Tried:

1. Created a 'Class Library' project with 'Linq to SQL added'

2. Added SQL connection with 'sql user name and password'. The app.config file as shown below.

<connectionStrings><add name="AdventureEntityClass.Properties.Settings.NorthwindConnectionString"
            connectionString="Data Source=myserver;Initial Catalog=Northwind;User Id=spsqlservice;Password=sqlpwd"
            providerName="System.Data.SqlClient" /></connectionStrings>

3. Compiled project. Created new project sharepoint visual web part

4. Added the above 'linq to sql' dll as a reference .

5. Added a feature activation/deactivation method to modify 'web.conifg' file with connection string.

6. Wrote below code ( as i thought straight forward) in webpart control file.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Web.UI.WebControls.WebParts;
using AdventureEntityClass;
using System.Linq;

using System.Text;
using System.Threading.Tasks;

namespace EntityVisualWebPart.VisualWebPart1
{
    [ToolboxItemAttribute(false)]
    public partial class VisualWebPart1 : WebPart
    {


        protected void Page_Load(object sender, EventArgs e)
        {
            AdventureClassDataContext adventureclass = new AdventureClassDataContext();

            var allemployees = (from employe in adventureclass.Employees
                               where employe.FirstName != null
                               select employe).ToList();

            GridView1.DataSource = allemployees;
                      
            GridView1.DataBind();
        }
    }
}

Though the code complied. But my grid view in webpart with no result and error.

My question :

1. what steps am I missing?

2. How to make sure the context class getting connection string from web.config file?

3. Do I need to create again entity frame work on top of LINQ to SQL as explained in below link.

http://fabiangwilliams.wordpress.com/2009/12/03/creating-a-sharepoint-2010-external-content-type-with-crud-methods-using-linq-and-a-sql-lob-system/

4. Can't I escape BDC entity model and BCS service application?

5. how to compile the connection string in LINQ to SQL if I use 'Secure Store service' for production environment.?

6. Does I need to implement impersonation method?

In simple. I  want to create a server side farm solution using 'LINQ to SQL ' class  without BCS service to do CRUD operations on SQL database using Visual Webpart?.

I want to achieve many to many relation ship and to use stored procedures and join mutliple SQL tables.

Please give with example code.

Murali Krishna Dittakavi *********************** If my answer/post resolved your query could you mark the post as answered. If it is helpful then vote as Helpful. Thanks