[C# net4] DropDownList disabled after change value

.NET
1

Hello guys, hope in your appreciated help.

It possible disable one DropDownList after changed the value in the same DropDownList?

How to intercept the change in DropDownList ?

my problem is:

I’ve one dropdownlist with or without selected value:

                    <asp:DropDownList ID="txt" runat="server" AutoPostBack="true" OnSelectedIndexChanged="Save_SelectedIndexChanged">
                    </asp:DropDownList>




private void txtDDL()
    {
        txt.Items.Clear();
        txt.Items.Add(new ListItem("------", ""));
        txt.Items.Add(new ListItem("A", "A"));
        txt.Items.Add(new ListItem("B", "B"));
        txt.Items.Add(new ListItem("C", "C"));
        txt.Items.Add(new ListItem("D", "D"));
        txt.AppendDataBoundItems = true;

        mySQL = "SELECT txt FROM dotable WHERE txt =  ? ";

        OdbcCommand objCmd =
            new OdbcCommand(mySQL, myConnectionString);
        objCmd.Parameters.AddWithValue("param1", dbDDL.SelectedItem.Value);
        objCmd.CommandType = CommandType.Text;
        objCmd.CommandText = mySQL;

        try
        {
            myConnectionString.Open();

            OdbcDataReader dr = objCmd.ExecuteReader();
            while (dr.Read())
            {
                if (dr["txt"].ToString() != "")
                {
                    txt.DataTextField = "txt";
                    txt.DataValueField = "txt";
                    txt.DataBind();
                    txt.SelectedValue = dr["txt"].ToString();

                    if (dr["txt"].ToString() == "A" || dr["txt"].ToString() == "B")
                    {
                        txt.Enabled = false;
                    }
                }
            }
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }
        finally
        {
            myConnectionString.Close();
        }
    }

when I select one new value of my txtDDL fired this event:

protected void Save_SelectedIndexChanged(object sender, EventArgs e)
{
OdbcCommand cmd = new OdbcCommand("update ....", myConnectionString);
cmd.Parameters.AddWithValue("param1", txtDDL.SelectedItem.Value);
cmd.Parameters.AddWithValue("param2", DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss"));
try
{
myConnectionString.Open();
cmd.ExecuteNonQuery();
cmd.Dispose();

StringBuilder sb = new StringBuilder();
sb.Append("<script language=javascript>\
");
sb.Append("alert("ok");
sb.Append("window.history.go(-1);\
");
sb.Append("\
</script>");
Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "MyScript", sb.ToString(), false);

}
finally
{
myConnectionString.Close();
}
}

when the event is fired and return to home page I need disable the dropDown List.

Any suggestion would be greatly appreciated
Thank you in advance

2

It may be better to add items in the page_load void then add the rest to the selectedindex void executing two SQL statements so the dropdownlist (txt) will have a value:

mySQL = "SELECT txt FROM dotable WHERE txt = ? ";

mySQL = “SELECT txt FROM dotable WHERE txt=” & txt.text & “;”;

3

So you enjoy getting SQL injected?