Question

We have a certain database that has some employee information, and I just wrote a small class to access some of this information. This class contains with it an application configuration file that has a connection string to the database. There is only 3 files in this project.
Two .cs files and one App.config file.

The app.config file has this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="connString" value="server=myserver;uid=mysa;pwd=mypwd;database=mydb"/>
  </appSettings>
</configuration>

One of my CS files I have a class like so:

namespace Employees.DAL
{

    public static class DAL
    {
        private static readonly string connString = System.Configuration.ConfigurationManager.AppSettings["connString"].ToString();


        public static Employee GetEmployeeByID(long EmpID)
        {
            Employee e = null;

            using (SqlConnection con = new SqlConnection(connString))
            {
                using (SqlCommand cmd = new SqlCommand("EMPDLL_selEmployeeByID", con))
                {
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.Parameters.Add("@LoginID", SqlDbType.BigInt).Value = EmpID;
                    con.Open();

                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        if (reader.HasRows)
                        {
                            if (reader.Read())
                            {   //todo: implement Employee class
                                e = new Employee((long)reader["LoginID"]
                                                );
                            }

                        }
                    }
                }
            }

            return e;
        }
    }
}

Fairly simple just grabs a record from the db and makes an employee out of it which is in the Employee.cs class:

namespace Employees.Objects
{
    public class Employee
    {
        /// <summary>
        /// ID of employee.
        /// </summary>
        public long LoginID { get; private set; }

        public Employee( long LoginID)
           {
            this.LoginID = LoginID;
           }
     }
}

Now what I did was create a new console project in vs2010 and I add a reference to this .dll file that I built, namely Employees. I need to do this because I have to write this as a reusable class so that others can include it.

So then I just did some simple console app like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Employees.DAL;
using Employees.Objects;

    namespace ConsoleEmployeesTest
    {
        class Program
        {
            static void Main(string[] args)
            {
                try
                {
                    Employee e = DAL.GetEmployeeByID(68); //fails right here...
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.ToString());
                }
                Console.ReadLine();
            }
        }
    }

I get an exception

System.TypeInitilizationException: the type initializer for Employees.DAL.DAL threw an

exception –> System.NullReferenceException: Object reference not set to an instance of an

object.

Is this because the new app does not see the app.config file?

Answer 1

Consider adding the configuration file as a resource to your DLL and then at run time read the value out of the resource instead.