Post back from Javascript: Can I link a postback to an Update Panel trigger?

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Hi All,

I have a javascript function in my aspx code calling __doPostBack() function. In my code behind for this post back I update a selected item in a drop down list control depending on other control's value. The functionality is working fine but the postback is rendering the entire page and it is slow. I want to use an Updatepanel so that I only re-render the drop down list. Is it possible to somehow add a trigger to an UpdatePanel to link to this postback like the trigger to link to an control event? Or is there another way to achieve this?

Thanks in advance.

Like this:

XML

<asp:UpdatePanel ID="UpdatePanel2" runat="server">
  <ContentTemplate>
      <asp:DropDownList ID="ddlItem1" runat="server" DataTextField="Item1" DataValueField="Item1">
      </asp:DropDownList>
  </ContentTemplate>
<Triggers>
      <asp:AsyncPostBackTrigger ControlID="ddlItem2" EventName="SelectedIndexChanged"/>
</Triggers>
</asp:UpdatePanel>

Posted 7-Aug-13 7:42am

Meg Takahashi

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Musakkhir · Answer 1 · 2013-08-07T13:47:00

Solution 1

1st method :: Javascript Code:

XML

function refreshddlItem2()
{
document.getElementById('<%= ddlItem2.ClientID %>').SelectedIndexChanged();
}

Add property to dropdownlist.

SQL

AutoPostBack="true"
onselectedIndexChanged="refreshddlItem2()"

2nd Method:

C#

protected void Page_PreRender(object sender, EventArgs e)
{

SQL

ClientScript.RegisterClientScriptBlock(typeof(Page), "UpdatePanelIDs", script, true);

}

3rd Method:
Add attributes to dropdownlist control and call the javascript function when it is necessary.

Posted 7-Aug-13 13:47pm

Musakkhir

Comments

Dholakiya Ankit 7-Aug-13 23:26pm

is it working?

Meg Takahashi 8-Aug-13 8:50am

Hi Musakkhir,
Thanks for your reply! I am not able to use the 'SelectedIndexChanged' event as I am using 'onBlur' attribute. So I cannot use the 1st method. I want to handle the function to update another ddl value on the server side, so 3rd method is not suitable for my needs. (I'm calling my __doPostBack() in this way though.) I'm not sure how exactly the 2nd method works, but I will see if it is something I can do. I will let you know how it goes.