ASP Form Dropdown OnSelectedIndexChanged event not working

Question

User2037455357 posted

Hello

I have dropdown OnselectionIndexChanged event

I want to change a label backcolor based on the Dropdown.SelectItem.value.

I have AutoPostBack="true" in the dropdown aspx

If I have no AutoPostBack in the aspx the c# event does not fire.

but when I go through the code on debug the selection is always the top value which I assume is due to the postback = true.

C# below.

if (DropDown.SelectedItem.Value == "value3")

            {
                Lbl.BackColor = Color.Red;
                Lbl.Text = "High";

            }

            else
            {
                Lbl.BackColor = Color.Green;
                Lbl.Text = "Low";



            }

But when I select the 3rd value the if statement always skips the condition and goes onto the else statement.

what am I doing wrong please

Regards

Rob

Answer 1

User2037455357 posted

Its ok, sorted it,

I wrapped my code within a isPostBack to cope with postbacks,

see below.

if (IsPostBack)
                return;

            {

if (DropDown.SelectedItem.Value == "value3")

            {
                Lbl.BackColor = Color.Red;
                Lbl.Text = "High";

            }

            else
            {
                Lbl.BackColor = Color.Green;
                Lbl.Text = "Low";



            }

}

Answer 2

User288213138 posted

Hi  masterdineen,

Have you solved your problem？
 
I tried to reproduce your problem and found that when I select 3rd value, the if statement was working normally.
 

Please check your code, if there are still problems, Please elaborate on your question.

The Reslut:

Answer 3

User2037455357 posted

Hi. Sameu<br>
<br>
I see you had the same result with or without using ispostback. i’m not sure how i managed to get
<br>
the incorrect result with my version. i know if i didn’t include postback: auto within the aspx code the event didn’t even fire off.
<br>
<br>
did you have postback: Auto within the dropdown aspx as well ?

Also if i didn’t use ispostback in the page load the dropdown selection would always
default to the first value in the dropdown

Answer 4

User-893317190 posted

Hi masterdineen,

Sam's code shows that no matte you write return or not in pageload , the selectedindexchange event will always fire.

Not sure why your event couldn't fire , a normal wring is

<form id="form1" runat="server" >
        <asp:DropDownList ID="DropDown" runat="server" AutoPostBack="true" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
            <asp:ListItem >value3</asp:ListItem>
            <asp:ListItem >value2</asp:ListItem>
            <asp:ListItem >value1</asp:ListItem>
        </asp:DropDownList>

        <asp:Label ID="Lbl" runat="server" Text="Label"></asp:Label>
    </form>

Code behind.

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (DropDown.SelectedItem.Value == "value3")

            {
                Lbl.BackColor = Color.Red;
                Lbl.Text = "High";

            }

            else
            {
                Lbl.BackColor = Color.Green;
                Lbl.Text = "Low";

            }

        }

Could you show your complete code? I am afraid your other code causes this problem.

Best regards,

Ackerly Xu

Answer 5

User2037455357 posted

this IS working now,

and is the same as your so thank you for your help