How to add and use connection string from App.Config file in Windows Application using C# and VB.Net

You need to add the System.Configuration reference in your project

App.Config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="ConString"
    connectionString="Data Source=AZEEM-HP;Initial Catalog=Sample;Integrated Security=True"/>
  </connectionStrings>
</configuration>

Add a Button and a Label in your Form. Add OnClick Event for Button.

Code to get the ConnectionString.

C#:

private void button1_Click(object sender, EventArgs e)
{
    this.label1.Text = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
}

VB.Net

Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.Click
    Me.label1.Text = ConfigurationManager.ConnectionStrings("ConString").ConnectionString
End Sub