Programatically update connectionstring using C#

var configuration = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("~");
var section = (System.Configuration.ConnectionStringsSection)configuration.GetSection("connectionStrings");

section.ConnectionStrings["MySqlConnection"].ConnectionString = "Data Source=" + 
        txtserver.Text + ";Initial Catalog=" + txtdatabase.Text + ";User ID=" + txtuid.Text + 
        ";Password=" + txtpwd.Text;
configuration.Save();