DropDownList in ASP.net pages has OnSelectedIndexChanged fire twice

Question

html

    <asp:DropDownList ID="ddlOffice" runat="server" Rows="10" Width="300px" AutoPostBack="true" OnSelectedIndexChanged="ddlOffice_SelectedIndexChanged" EnableViewState="true"   />

Even though according to MSDN I am doing everything correctly. the SelectedIndexChanged still fires twice. Any ideas how this can fixed?

Answer 1

One possible reason: If you have a also registered the event handler in codebehind(f.e. via Handles clause in VB.NET or += in C#) it will cause the event to be fired twice.

Then you just have to remove one of it, for example on aspx:

<asp:DropDownList ID="ddlOffice" 
    runat="server" Rows="10" Width="300px"
    AutoPostBack="true" 
    EnableViewState="true"   />