Calling Connection string from App setings app.config file to C# code

Question

I'm trying to call a connection string from the app.config file to C# code. This is the app.config code:

<?xml version="1.0" encoding="utf-8" ?>
  <configuration>
 <appSettings>

<add key="connectstring" value="Data Source=server111;Initial Catalog=database1;        Integrated Security=False;Persist Security Info=False; User ID=username;Password=password;Encrypt=True; TrustServerCertificate=True; MultipleActiveResultSets=True"/>

 </appSettings>
</configuration>

This is the C# code:

  private SqlConnection connStudent;  
  connStudent = new SqlConnection(ConfigurationManager.AppSettings["connectstring"].ToString());
  connStudent.Open();

The code should be right, but I'm getting a Null Reference Exception, and while debugging the program, connStudent is always null and does not get the connection string . The error is "Object reference not set to an instance of an object".

I don't think this solves your issue, but I believe the 'value' from app.config is already being returned as a string so there is no need for ToString(). — Nashibukasan, May 24 '12 at 05:15
The C# code you show is not compilable or even valid, so at least provide the full stacktrace of the exception to better figure where it "might" have been raised at. As of now it is most likely that 'connectstring' is not found in your appSettings and thus `AppSettings["connectstring"]` returns `null`. So make sure that your `app.config` file is actually "build into" the output directory, next to your executable, bearing the same name (like "my.exe.config"). — Christian.K, May 24 '12 at 05:20

score 3 · Answer 1 · edited May 24 '12 at 05:27

3

if you are using .NET 2.0 or above Use following

<connectionStrings>
<add name="myConnectionString" connectionString="server=localhost;database=myDb;uid=myUser;password=myPass;" />
</connectionStrings>

and then

string connStr = ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString;

edited May 24 '12 at 05:27

Christian.K

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answered May 24 '12 at 05:14

Pete

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1

Why the limitation on .NET 3.5+? The `ConfigurationManager.ConnectionStrings` property was available since .NET 2.0. – Christian.K May 24 '12 at 05:17
Still null. Object reference not set to an instance of an object. – user919789 May 24 '12 at 06:19
Have you added ref to System.Configuration ? – Pete May 24 '12 at 10:36

score 0 · Answer 2 · answered May 24 '12 at 05:29

your code is fine. check to make sure your copy to output directory property is set to copy always or copy if newer. if that still doesn't work, try to delete temp obj files.

the following test code works fine.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="connectstring" value="Data Source=server111;Initial Catalog=database1;        Integrated Security=False;Persist Security Info=False; User ID=username;Password=password;Encrypt=True; TrustServerCertificate=True; MultipleActiveResultSets=True"/>
  </appSettings>
</configuration>

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                SqlConnection connStudent;
                connStudent = new SqlConnection(ConfigurationManager.AppSettings["connectstring"].ToString());
                //connStudent.Open();
                //connStudent.Close();
                Console.WriteLine("ok");
            }
            catch
            {
                Console.WriteLine("error");
            }
        }

    }
}

Calling Connection string from App setings app.config file to C# code

2 Answers2

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