Populate TextBox from SQL Server Database in ASP.Net Wizard control

Check this sample

<asp:Wizard ID="Wizard1" runat="server">
    <WizardSteps>
        <asp:WizardStep ID="WizardStep1" runat="server" Title="Step 1">
            <asp:TextBox ID="textCC" runat="server"></asp:TextBox></asp:WizardStep>
        <asp:WizardStep ID="WizardStep2" runat="server" Title="Step 2">
            <asp:TextBox ID="Textbox1" runat="server" Text='test'></asp:TextBox></asp:WizardStep>
    </WizardSteps>
</asp:Wizard>

    protected void Page_Load(object sender, EventArgs e)
    {
        string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        string query = "SELECT ContactName FROM Customers where CustomerId='ALFKI'";
        SqlCommand cmd = new SqlCommand(query);
        using (SqlConnection con = new SqlConnection(conString))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataSet ds = new DataSet())
                {
                    sda.Fill(ds);
                    textCC.Text = ds.Tables[0].Rows[0]["ContactName"].ToString();
                }
            }
        }
      }