private void button1_Click(object sender, EventArgs e)
{
string con = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
SqlConnection cont = new SqlConnection(con);
try
{
cont.Open();
System.Windows.Forms.MessageBox.Show("Sucess");
}
catch (Exception ed)
{
MessageBox.Show("Unsucess" + ed.Message);
}
}
also change you config file
<configuration>
<connectionStrings>
<add name="ConnectionString" connectionString="Data Source=A01hw306775\SQLEXPRESS;Initial Catalog=NorthWind;Integrated Security=True" />
</connectionStrings>
</configuration>