select gridview single row after that all values of gridview come to textbox of form

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            BindData();
        }
 
    }
 

private void BindData()
    {
        string constr = @"Data Source=SQLEXPRESS2008;Initial Catalog=database_name;Integrated Security=True";
        string query = "SELECT 1st_column,2nd_column,3rd_column FROM Table_Name";
        SqlDataAdapter da = new SqlDataAdapter(query, constr);
        DataTable table = new DataTable();
        da.Fill(table);
        GridView1.DataSource = table;
        GridView1.DataBind();
 
    }

protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
    {
        GridView1.EditIndex = e.NewEditIndex;
        BindData();
    }
 
protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        e.Cancel = true;
        GridView1.EditIndex = -1;
        BindData();
    }
 
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        GridViewRow row = GridView1.Rows[e.RowIndex];
        
        TextBox txt1st_column = (TextBox)row.FindControl("txt1st_column");	
        TextBox txt2nd_column = (TextBox)row.FindControl("txt2nd_column");
        TextBox txt3rd_column = (TextBox)row.FindControl("txt3rd_column");   

        int a = Int32.Parse(GridView1.DataKeys[e.RowIndex].Value.ToString());
        string b = txt2nd_column.Text;
        string c = txt3rd_column.Text;
 
        UpdateProduct(a, b,c);
 
    }
 
private void UpdateProduct(int a, string b,string c)
    {
        try
        {
            string constr = @"Data Source=SQLEXPRESS2008;Initial Catalog=Database;Integrated Security=True";
            string query = "UPDATE Table_Name SET 2nd_column = @b, 3rd_column = @c WHERE 1st_column = @a";
 

            SqlConnection con = new SqlConnection(constr);
            SqlCommand com = new SqlCommand(query, con);
 
            com.Parameters.Add("@a", SqlDbType.Int).Value = 1st_column;
            com.Parameters.Add("@b", SqlDbType.NVarChar).Value = 2nd_column;
            com.Parameters.Add("@c", SqlDbType.NVarChar).Value = 3rd_column;
 

            con.Open();
            com.ExecuteNonQuery();
            con.Close();
 

            GridView1.EditIndex = -1;
            BindData();
        }
        catch (Exception ex)
        {
            throw ex;
    }
 
protected void btn_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
	try
	{
	string constr = @"Data Source=SQLEXPRESS2008;Initial Catalog=Database;Integrated Security=True";
	string query = "DELETE FROM Table_Name WHERE 1st_column=@a";
 
	SqlConnection con = new SqlConnection(constr);
	SqlCommand cmd = new SqlCommand();
 
	cmd.Parameters.Add("@a", SqlDbType.Int).Value = Convert.ToInt32(GridView1.Rows[e.RowIndex].Cells[1].Text)";
	cmd.Connection = con;
 
	con.Open();
	cmd.ExecuteNonQuery();
 
	con.Close();
	BindData();
	}
	catch(Exception ex)
	{
	    throw ex;
	}
  }