Connection String in ASP.Net with C#

Connection String in ASP.Net with C#:

Web Config

	<connectionStrings>
		<add name="Master" connectionString="Data Source=10.155.44.11;Initial Catalog=Master;User Id=ta;Password=xxxxx" providerName="System.Data.SqlClient"  />
	</connectionStrings>

C# Coding:

  public void setconnectionstring()
    {
        try
        {
            str = System.Configuration.ConfigurationManager.ConnectionStrings["Master"].ToString();
        }
        catch(Exception ex)
        {
            Response.Write(ex.ToString());
        }
    }
    
    protected void Button1_Click(object sender, EventArgs e)
    {
    setconnectionstring();
    SqlConnection con = new SqlConnection(str);
    con.Open();
    SqlCommand cmd = new SqlCommand("select * from phone_entries", con);
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    con.close();
    }