Gridview row updating

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
    Label lb = (Label)GridView1.Rows[e.RowIndex].FindControl("Label6");
    DropDownList ddl = (DropDownList)GridView1.Rows[e.RowIndex].FindControl("DropDownList1");
    RadioButtonList rbl = (RadioButtonList)GridView1.Rows[e.RowIndex].FindControl("RadioButtonList1");
    CheckBoxList chb = (CheckBoxList)GridView1.Rows[e.RowIndex].FindControl("CheckBoxList2");
    TextBox tx1 = (TextBox)GridView1.Rows[e.RowIndex].FindControl("TextBox1");
    TextBox tx2 = (TextBox)GridView1.Rows[e.RowIndex].FindControl("TextBox2");
    TextBox tx3 = (TextBox)GridView1.Rows[e.RowIndex].FindControl("TextBox3");
    ListBox llb = (ListBox)GridView1.Rows[e.RowIndex].FindControl("ListBox1");
    string ski = "";
    foreach (ListItem selectedItem in chb.Items)
    {
        if (selectedItem.Selected)
        {
            if (ski.Length == 0)
                ski = selectedItem.Value;
            else
                ski = ski + "," + selectedItem.Value;
        }
    }

    string pro = "";
    foreach (ListItem selectedItem in llb.Items)
    {
        if (selectedItem.Selected)
        {
            if (pro.Length == 0)
                pro = selectedItem.Value;
            else
                pro = pro + "," + selectedItem.Value;

        }
    }
    sqlcon = new SqlConnection(con);
    sqlcon.Open();
    string sql = "update empdetails set empname='" + tx1.Text + "',empcode='" + tx2.Text + "',department='" + ddl.SelectedValue.ToString() + "',salary='" +
    tx3.Text + "',gender='" +
    rbl.SelectedValue.ToString() + "',skill='" + ski + "',project='" + pro + "' where empno='" + lb.Text + "'";
    SqlCommand cmd = new SqlCommand(sql);
    cmd.CommandType = CommandType.Text;
    cmd.Connection = sqlcon;
    cmd.ExecuteNonQuery();
    GridView1.EditIndex = -1;
    showgrid();
}