registration with validations

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Data.SqlClient;

public partial class registration : System.Web.UI.Page

{

   SqlConnection con = new SqlConnection("Data Source=AAPTI-1506A06CD\\AAPTI;Initial Catalog=vidya;Integrated Security=True");

   protected void Page_Load(object sender, EventArgs e)

   {

       if (!IsPostBack)

       {

          

           DropDownList1.Items.Add("--select--");

           try

           {

               SqlCommand cmd = new SqlCommand("select CountryName from country", con);

               con.Open();

               SqlDataReader dr;

               dr = cmd.ExecuteReader();

               while (dr.Read())

               {

                   DropDownList1.Items.Add(dr[0].ToString());

               }

               con.Close();

           }

           catch (Exception ex)

           {

               Response.Write(ex);

           }

       }

   }

   protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

   {

       if (DropDownList1.SelectedIndex > 0)

       {

           try

           {

               SqlCommand cmd = new SqlCommand("select Countrycode from country where CountryName='" + DropDownList1.SelectedValue.ToString() + "' ", con);

               SqlDataReader dr;

               con.Open();

               dr = cmd.ExecuteReader();

               while (dr.Read())

               {

                   txtcode.Text = dr.GetValue(0).ToString();

               }

               con.Close();

           }

           catch (Exception ex)

           {

               Response.Write(ex);

           }

       }

       else

           txtcode.Text = "";

   }

   protected void btnSubmit_Click(object sender, EventArgs e)

   {

       if (DropDownList1.SelectedIndex > 0)

       {

           string mobile = txtcode.Text + txtphno.Text;

           SqlConnection con = new SqlConnection("Data Source=AAPTI-1506A06CD\\AAPTI;Initial Catalog=vidya;Integrated Security=True");

           try

           {

               SqlCommand cmd = new SqlCommand("insert into Registration values('" + txtName.Text + "','" + txtEmail.Text + "','" + txtPW.Text + "','" + txtCPW.Text + "','" + DropDownList1.SelectedItem.Text + "','" + mobile.ToString() + "')", con);

               con.Open();

               int i = cmd.ExecuteNonQuery();

               if (i > 0)

               {

                   ShowAlertMessage(i + " Row has been Inserted Successfully");

               }

               con.Close();

               ClearTextboxes(this.Controls);

           }

           catch (Exception ex)

           {

               Response.Write(ex);

           }

       }

       else

           ShowAlertMessage("Please select a Country");

   }

   public void ShowAlertMessage(string error)

   {

       Page page = HttpContext.Current.Handler as Page;

       if (page != null)

       {

           error = error.Replace("'", "\'");

           ScriptManager.RegisterStartupScript(page, page.GetType(), "err_msg", "alert('" + error + "');", true);

       }

   }

   public void ClearTextboxes(ControlCollection ctrl)

   {

       foreach (Control c in ctrl)

       {

           //Clearing text in the TextBox

           if (c is TextBox)

               ((TextBox)c).Text = string.Empty;

           //Clearing Selected RadioButton

           if (c is RadioButtonList)

               ((RadioButtonList)c).ClearSelection();

           //Clearing selected ListBox

           if (c is ListBox)

               ((ListBox)c).ClearSelection();

           //Clearing selected CheckBox

           if (c is CheckBox)

               ((CheckBox)c).Checked = false;

           //Clearing selected index of DropDown

           if (c is DropDownList)

               //usually dorpdownlists 0 index is used for "- Select -", "- Apply -" etc.  

               ((DropDownList)c).SelectedIndex = 0;

           //(myControl as DropDownList).SelectedIndex = 0;

           ClearTextboxes(c.Controls);

       }

   }

}