Issue with UpdatePanel

Question

User1769015664 posted

Why does the following code make the entire screen flash when either of the dropdown is clicked?

<asp:UpdatePanel ID="UpdatePanel5" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
    <td style="width:10%;"><asp:DropDownList ID="DropDownList1" runat="server" Width="95%" AutoPostBack="true" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged"></asp:DropDownList></td>
    <td style="width:10%;"><asp:DropDownList ID="DropDownList2" runat="server" Width="95%" AutoPostBack="true"  OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged"></asp:DropDownList></td>
    </ContentTemplate>
</asp:UpdatePanel>

Answer 1

User-1838255255 posted

Hi NJ2,

About how to use dropdownlist inside updatepanel, I make a sample, the page is not refresh when I click the dropdownlist. Please check the following code:

Sample Code:

 <asp:ScriptManager ID="ScriptManager1" runat="server">
 </asp:ScriptManager>
 <asp:UpdatePanel ID="upSetSession" runat="server">
            <ContentTemplate>
                <asp:DropDownList ID="ddlMyList" runat="server"
                    OnSelectedIndexChanged="ddlMyList_SelectedIndexChanged"
                    AutoPostBack="true">
                    <asp:ListItem>Select One</asp:ListItem>
                    <asp:ListItem>Maybe</asp:ListItem>
                    <asp:ListItem>Yes</asp:ListItem>
                </asp:DropDownList>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="ddlMyList"
                    EventName="SelectedIndexChanged" />
            </Triggers>
 </asp:UpdatePanel>

protected void Page_Load(object sender, EventArgs e)
        {

        }
protected void ddlMyList_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

Best Regards,

Eric Du

Answer 2

User1769015664 posted

Thanks Eric but it doesn't work right. I have posted this question weeks ago and have already tried your solution above previous and just tried again. It adds tow new dropdowns right above when I click on one of the dropdowns. Please see attached screenshot.

Answer 3

User-1838255255 posted

Hi NJ2,

According to your description, I think this new issue(Extra Dropdownlist created when click Dropdownlist) is not related your previous issue(screen flash).

This issue is related to the dropdownlist click or selectchange or Page_Load event. So you need change these events if have code to create a new dropdownlist.

Best Regards,

Eric Du

Answer 4

User1769015664 posted

Eric,

Adding the Trigger has always been issue in my case and this is the 2nd post within 4 weeks. I do not have any code 

This issue is related to the dropdownlist click or selectchange or Page_Load event. So you need change these events if have code to create a new dropdownlist.

All I have in SelectChange is [string sString ="Got it"]

Answer 5

User1769015664 posted

Eric, there was an obvious mistake in my code above; the update panel needed to be inside <TD> element. 

It seems to be working fine; I will give you credit for your answer to actual question.