System.TypeInitializationException when referencing dll

Question

I'm trying to create a Data Framework in the form of a .dll so that I can reference it when creating new projects, as opposed to reinventing the wheel with each project I create.

I have an app.config in which I store my SQL connections, a class that uses the app.config to build my SQL ConnectionString (ConnectionStrings.cs) and a Logic class (Logic.cs) that'll build whatever objects I require from the SQL Server.

Here's the classes in the .dll:

ConnectionStrings.cs:

using System.Configuration;
using System.Data.SqlClient;

namespace DataFramework
{
    public static class ConnectionStrings
    {
        static string _liveConnectionString = ConfigurationManager.ConnectionStrings["LiveDataSource"].ConnectionString;
        static string _liveMISConnectionString = ConfigurationManager.ConnectionStrings["LiveDataSource_MIS"].ConnectionString;
        static string _devConnectionString = ConfigurationManager.ConnectionStrings["DevDataSource"].ConnectionString;
        static string _devMISConnectionString = ConfigurationManager.ConnectionStrings["DevDataSource_MIS"].ConnectionString;

        public static SqlConnection CreateLiveConnection
    {
        get { return new SqlConnection(_liveConnectionString); }
    }

    public static SqlConnection CreateLiveMISConnection
    {
        get { return new SqlConnection(_liveMISConnectionString); }
    }

    public static SqlConnection CreateDevConnection
    {
        get { return new SqlConnection(_devConnectionString); }
    }

    public static SqlConnection CreateDevMISConnection
    {
        get { return new SqlConnection(_devMISConnectionString); }
    }
  }
}

Logic.cs:

using System;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;

namespace DataFramework
{
    public class Logic
    {

    SqlConnection liveConnection = ConnectionStrings.CreateLiveMISConnection;
    SqlConnection devMISConnection = ConnectionStrings.CreateDevMISConnection;

    public bool IsConnecting { get; set; }
    public string ConnectionMessage { get; set; }

    public async Task<DataTable> ResultDataTable(bool connectToLive, string commandText, CommandType commandType)
    {
        DataTable dt = new DataTable();
        using (SqlCommand command = new SqlCommand())
        {
            try
            {
                command.CommandType = commandType;
                command.CommandTimeout = 360000000;

                switch (connectToLive)
                {
                    case true:
                        command.CommandText = commandText;

                        command.Connection = liveConnection;

                        if (liveConnection.State == ConnectionState.Connecting)
                        {
                            IsConnecting = true;
                            ConnectionMessage = "Connecting to Data Source...";
                        }
                        if (liveConnection.State != ConnectionState.Closed)
                            liveConnection.Close();
                        if (liveConnection.State != ConnectionState.Open)
                        {
                            liveConnection.Open();
                            IsConnecting = false;
                            ConnectionMessage = "";
                        }
                        break;
                    case false:
                        command.CommandType = commandType;
                        command.CommandText = "";
                        command.Connection = devMISConnection;
                        if (devMISConnection.State == ConnectionState.Connecting)
                        {
                            IsConnecting = true;
                            ConnectionMessage = commandText;
                        }
                        if (devMISConnection.State != ConnectionState.Closed)
                            devMISConnection.Close();
                        if (devMISConnection.State != ConnectionState.Open)
                        {
                            devMISConnection.Open();
                            IsConnecting = false;
                            ConnectionMessage = "";
                        }
                        break;
                }

                using (SqlDataReader reader = await command.ExecuteReaderAsync())
                {
                    dt.Load(reader);
                }

            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message, "An Error Has Occured", System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Error);
            }
            finally
            {
                if (devMISConnection.State != ConnectionState.Closed)
                    devMISConnection.Close();

                if (liveConnection.State != ConnectionState.Closed)
                    liveConnection.Close();
            }
        }

        return dt;

    }
}
}

I include this dll as a reference in the app that I'm writing:

using System.Data;
using System.Threading.Tasks;
using System.Windows.Forms;
using DataFramework;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
    DataTable dt = new DataTable();
    DataFramework.Logic logic = new Logic();

    public Form1()
    {
        InitializeComponent();
    }

    private async void Form1_Load(object sender, EventArgs e)
    {
        dt = await Task.Run(() => logic.ResultDataTable(true, "SELECT * FROM MIS.dbo.ETL_Table", CommandType.StoredProcedure));
    }
}
}

The code throws the exception here:

SqlConnection liveConnection = ConnectionStrings.CreateLiveMISConnection;

So why, when I'm initializing the class, do I get this issue?

Answer 1

When you reference a DLL (or project) from another project, the app.config from the top most project is used. So, if you have your DataFramework being called from your WinformsApp, then your WinformsApp needs to have the right config settings in it. By default, it will ignore any app.config in the DataFramework. A bit frustrating at times! Copy your settings from your DataFramework app.config in to the WinformsApp app.config and it will work.

Another unrelated observation is that you have the following:

"SELECT * FROM MIS.dbo.ETL_Table", CommandType.StoredProcedure

The command type should be text and not a stored procedure.