In this article I will explain with an example, how to read (get) Connection String from App.Config file using C# and VB.Net in .Net 4.5.
In Windows applications, Class Library or Console applications one has to reference the System.Configuration Assembly in order to read Connection String value from the App.Config file.
Adding ConnectionString to the App.Config file
You need to add the Connection String in the ConnectionStrings section of the App.Config file in the following way.
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="ConString" connectionString="Data Source=Mudassar-PC\SQL2005;Initial Catalog=Northwind;Integrated Security=true" />
</connectionStrings>
</configuration>
Adding System.Configuration reference
The very first thing you need to do is to add reference of the System.Configuration Assembly to the project in the following way.
1. Right click on the References and click Add Reference option from the Context Menu.
2. From the Add Reference dialog box, click on Assemblies Tab and look for System.Configuration assembly. Once you find it simply select and click OK.
3. Once the reference is added, it will be shown in the References folder of the Solution Explorer.
Namespaces
You will need to import the following namespace.
C#
using System.Configuration;
VB.Net
Imports System.Configuration
Reading ConnectionString from App.Config file using C# and VB.Net
Once the reference is added, you can read the Connection String value from the App.Config file in the following way.
C#
string connectionString = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
VB.Net
Dim connectionString As String = ConfigurationManager.ConnectionStrings("ConString").ConnectionString