尝试从web.config获取连接字符串时抛出NullReferenceException

Question

I am trying to implement NLayering in my asp.net mvc 5 application and have separated the application into different layers, one being the data access layer(DAL). In my DAL when I try to access the connection string in my Insert method I get a NullReferenceException. I have added the System.Configuration reference to my DAL project and a web.config file containing the ff code.

web.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
<add name="JcSpaceConnectionString" connectionString="Data Source=localhost;Initial Catalog=JcSpaceDatabase;Integrated Security=True;" providerName="System.Data.SqlClient" />
</connectionStrings>
</configuration>

JcSpaceDAL.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;
using JcSpaceEntities;

namespace JcSpaceDAL
{
    public class JcSpaceDAL
    {

        public static void Insert(JcSpaceAccount accountInfo)
        {
            string connectionString =    ConfigurationManager.ConnectionStrings["JcSpaceConnectionString"].ConnectionString;//This line causes the nullreferenceexception
            SqlConnection conn;
            SqlCommand cmd;
            using (conn = new SqlConnection(connectionString))
            using (cmd = new SqlCommand("spInsert")) {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@Name",   accountInfo.FirstName.ToString()+""+ accountInfo.LastName.ToString());
                cmd.Parameters.AddWithValue("@Email", accountInfo.Email);
                cmd.Parameters.AddWithValue("@DateOfBirth", acco    untInfo.DateOfBirth);
                cmd.ExecuteNonQuery();
            }


        }
    }
}

Why does it cause this?

Answer 1

I am guessing that you added the JcSpaceConnectionString to the wrong web.config file. Did you add the web.config file to your DAL project? If so you'll need to move it to the MVC project instead.