ConfigurationManager is not available

Question

I am trying to add the ConfigurationMangager in my programm. I've already tried to add the System.Configuration and System.Configuration.Install reference but nothing works. Is there any other way I could fix this problem?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Configuration;

namespace Gmos.Halbtax.Models
{
    static class Program
    {
        public static void connectDB()
        {
            string connString = ConfigurationManager.AppSettings["ConnString"].ToString();
            SqlConnection conn = new SqlConnection(connString);          
        }
    }
}

Answer 1

Make Sure Target framework is NET framework 4 and the version you select for System.Configuration is v4.0.0.0

Add System.Configuration in your project by clicking add Reference on your project

To check go to your Project Properties -> Application -> Target framework

Hope this will hep you.