Question

I want to retrieve the ConnectionString from the app.config in the DataAccess class library for use in Entity Framework’s .edmx model of the application by using this code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;

namespace BusinessLogicAndData
{
    public class Connection
    {
        public static RevenueData GetContext()
        {
            //ConfigurationManager configManager = new ConfigurationManager();
            string conString = ConfigurationManager.ConnectionStrings["RevenueData"].ConnectionString;

            RevenueData RDC = new RevenueData(conString);

            return RDC;
        }
    }
}

But each time the program runs, it throws a null reference exception complaining that

object reference is not set to an instance of an object

I have walked through the stack trace of the VS 2010 but I can’t seem to pinpoint the problem. Please any suggestions about the origin of the exception.

Answer 1

You should add connection string to App.Config of your executable application (not to config in DataAccess library project).