Add Edit Delete Search Clear Button C sharpe coding

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;


public partial class Add_New_PO : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection scon = new SqlConnection("Data Source=Tahir-PC;Initial Catalog=Shipping;Integrated Security=True");
        SqlCommand scmd = new SqlCommand("select PO from PO_Table" , scon);
        SqlDataAdapter sda = new SqlDataAdapter(scmd);
        DataSet ds = new DataSet();
        //DataTable dt = new DataTable();      
        sda.Fill(ds);
              
        if (TextBox1.Text == ds.Tables[0].Rows[0][0].ToString())
        {
            Response.Write("PO already Enter");
        }   
        else
        {

            SqlConnection use = new SqlConnection(" Data Source=Tahir-PC;Initial Catalog=Shipping;Integrated Security=True ");
            SqlDataAdapter da = new SqlDataAdapter();
            da.InsertCommand = new SqlCommand("insert into PO_Table values (@PO, @Style_Ref, @Price, @Season, @Order_Qty, @PO_Ship_Date, @PO_Shipping_Month, @PO_Shipping_Mode, @PO_Value, @PO_Destination)", use);
            da.InsertCommand.Parameters.Add("@PO", SqlDbType.Int).Value = TextBox1.Text;
            da.InsertCommand.Parameters.Add("@Style_Ref", SqlDbType.NVarChar).Value = TextBox2.Text;
            da.InsertCommand.Parameters.Add("@PO_Destination", SqlDbType.NVarChar).Value = DropDownList3.Text;
            da.InsertCommand.Parameters.Add("@Price", SqlDbType.Money).Value = TextBox3.Text;
            da.InsertCommand.Parameters.Add("@Season", SqlDbType.NVarChar).Value = DropDownList2.Text;
            da.InsertCommand.Parameters.Add("@Order_Qty", SqlDbType.Int).Value = TextBox4.Text;
            da.InsertCommand.Parameters.Add("@PO_Ship_Date", SqlDbType.DateTime).Value = TextBox5.Text;
            da.InsertCommand.Parameters.Add("@PO_Shipping_Month", SqlDbType.Char).Value = TextBox6.Text;
            da.InsertCommand.Parameters.Add("@PO_Shipping_Mode", SqlDbType.Char).Value = TextBox7.Text;
            da.InsertCommand.Parameters.Add("@PO_Value", SqlDbType.Int).Value = TextBox8.Text;
            use.Open();
            da.InsertCommand.ExecuteNonQuery();
            use.Close();
            TextBox1.Text = "";
            TextBox2.Text = "";
            TextBox3.Text = "";
            TextBox4.Text = "";
            TextBox5.Text = "";
            TextBox6.Text = "";
            TextBox7.Text = "";
            TextBox8.Text = "";
       
           
                  
           
            }
       

       
         scon.Close();


      
    }
    protected void Button2_Click(object sender, EventArgs e)
    {
        TextBox1.Text = "";
        TextBox2.Text = "";
        TextBox3.Text = "";
        TextBox4.Text = "";
        TextBox5.Text = "";
        TextBox6.Text = "";
        TextBox7.Text = "";
        TextBox8.Text = "";
    }
    protected void Button3_Click(object sender, EventArgs e)
    {
        SqlConnection scon = new SqlConnection("Data Source=Tahir-PC;Initial Catalog=Shipping;Integrated Security=True");
        SqlCommand scmd = new SqlCommand("select * from PO_Table", scon);
        SqlDataAdapter sda = new SqlDataAdapter(scmd);
        DataTable dt = new DataTable();
        sda.Fill(dt);

        if (TextBox1.Text == dt.Rows[0][0].ToString())
        {
            TextBox1.Text = dt.Rows[0][0].ToString();
            TextBox2.Text = dt.Rows[0][1].ToString();
            TextBox3.Text = dt.Rows[0][2].ToString();
            TextBox4.Text = dt.Rows[0][4].ToString();
            TextBox5.Text = dt.Rows[0][5].ToString();
            TextBox6.Text = dt.Rows[0][6].ToString();
            TextBox7.Text = dt.Rows[0][7].ToString();
            TextBox8.Text = dt.Rows[0][8].ToString();
            DropDownList2.Text = dt.Rows[0][3].ToString();
            DropDownList3.Text = dt.Rows[0][9].ToString();

        }
        else
        {
            Response.Write("PO Not Found");

        }
        scon.Close();


    }

    protected void Button4_Click(object sender, EventArgs e)
    {
        SqlConnection use = new SqlConnection(" Data Source=Tahir-PC;Initial Catalog=Shipping;Integrated Security=True ");
        SqlDataAdapter da = new SqlDataAdapter();
        da.UpdateCommand = new SqlCommand("update PO_Table set PO=@PO, Style_Ref=@Style_Ref, Price=@Price, Season=@Season, Order_Qty=@Order_Qty, PO_Ship_Date=@PO_Ship_Date, PO_Shipping_Month=@PO_Shipping_Month, PO_Shipping_Mode=@PO_Shipping_Mode, PO_Value=@PO_Value, PO_Destination=@PO_Destination where PO=@PO", use);
        da.UpdateCommand.Parameters.Add("@PO", SqlDbType.Int).Value = TextBox1.Text;
        da.UpdateCommand.Parameters.Add("@Style_Ref", SqlDbType.NVarChar).Value = TextBox2.Text;
        da.UpdateCommand.Parameters.Add("@PO_Destination", SqlDbType.NVarChar).Value = DropDownList3.Text;
        da.UpdateCommand.Parameters.Add("@Price", SqlDbType.Money).Value = TextBox3.Text;
        da.UpdateCommand.Parameters.Add("@Season", SqlDbType.NVarChar).Value = DropDownList2.Text;
        da.UpdateCommand.Parameters.Add("@Order_Qty", SqlDbType.Int).Value = TextBox4.Text;
        da.UpdateCommand.Parameters.Add("@PO_Ship_Date", SqlDbType.DateTime).Value = TextBox5.Text;
        da.UpdateCommand.Parameters.Add("@PO_Shipping_Month", SqlDbType.Char).Value = TextBox6.Text;
        da.UpdateCommand.Parameters.Add("@PO_Shipping_Mode", SqlDbType.Char).Value = TextBox7.Text;
        da.UpdateCommand.Parameters.Add("@PO_Value", SqlDbType.Int).Value = TextBox8.Text;
       
        use.Open();
        da.UpdateCommand.ExecuteNonQuery();
        use.Close();
        TextBox1.Text = "";
        TextBox2.Text = "";
        TextBox3.Text = "";
        TextBox4.Text = "";
        TextBox5.Text = "";
        TextBox6.Text = "";
        TextBox7.Text = "";
        TextBox8.Text = "";
    }
    protected void Button5_Click(object sender, EventArgs e)
    {
        SqlConnection use = new SqlConnection(" Data Source=Tahir-PC;Initial Catalog=Shipping;Integrated Security=True ");
        SqlDataAdapter da = new SqlDataAdapter();
        da.DeleteCommand = new SqlCommand("delete from PO_Table where PO=@PO", use);
        da.DeleteCommand.Parameters.Add("@PO", SqlDbType.Int).Value = TextBox1.Text;
        da.DeleteCommand.Parameters.Add("@Style_Ref", SqlDbType.NVarChar).Value = TextBox2.Text;
        da.DeleteCommand.Parameters.Add("@PO_Destination", SqlDbType.NVarChar).Value = DropDownList3.Text;
        da.DeleteCommand.Parameters.Add("@Price", SqlDbType.Money).Value = TextBox3.Text;
        da.DeleteCommand.Parameters.Add("@Season", SqlDbType.NVarChar).Value = DropDownList2.Text;
        da.DeleteCommand.Parameters.Add("@Order_Qty", SqlDbType.Int).Value = TextBox4.Text;
        da.DeleteCommand.Parameters.Add("@PO_Ship_Date", SqlDbType.DateTime).Value = TextBox5.Text;
        da.DeleteCommand.Parameters.Add("@PO_Shipping_Month", SqlDbType.Char).Value = TextBox6.Text;
        da.DeleteCommand.Parameters.Add("@PO_Shipping_Mode", SqlDbType.Char).Value = TextBox7.Text;
        da.DeleteCommand.Parameters.Add("@PO_Value", SqlDbType.Int).Value = TextBox8.Text;

        use.Open();
        da.DeleteCommand.ExecuteNonQuery();
        use.Close();
        TextBox1.Text = "";
        TextBox2.Text = "";
        TextBox3.Text = "";
        TextBox4.Text = "";
        TextBox5.Text = "";
        TextBox6.Text = "";
        TextBox7.Text = "";
        TextBox8.Text = "";
    }
}