Server Event for HTML Select control

问题

How can I add a server event for an HTML Select control?

HTML code is like this:

<div class="ui-widget">
    <select id="Select1" runat="server">
        <option>Select one...</option>
        <option>ActionScript</option>
        <option>AppleScript</option>
        <option>Asp</option>
        <option>BASIC</option>
    </select>
</div>

C# code is like this:

public void Select1_SomethingChange(object sender, EventArgs e)
{
    //random code
}

Now I know just as is it won't work, the 2nd line of the HTML needs an attribute of some kind.. I already tried the only 2 I could find which are these two below

<select id="Select1" runat="server" onServerChanged="Select1_SomethingChange">
<select id="Select1" runat="server" onSelectedIndexChanged="Select1_SomethingChange">

The problem is that the first options event never fires, and the 2nd option just doesn't exist. Please help me out here, any help is welcome.

回答1:

When you add runat="server" to an otherwise normal HTML element, it becomes an HtmlControl in the server-side code. Which doesn't expose a lot of events. In order to get richer server-side eventing, you need to use the ASP.NET controls. In this case that would be a DropDownList, which has the events you're looking for.

Something like this:

<div class="ui-widget">
    <asp:DropDownList id="Select1" OnSelectedIndexChanged="Select1_SomethingChange" runat="server">
        <asp:ListItem Selected="True" Value="White"> White </asp:ListItem>
        <asp:ListItem Value="Select one...">Select one...</asp:ListItem>
        <asp:ListItem Value="ActionScript">ActionScript</asp:ListItem>
        <asp:ListItem Value="AppleScript">AppleScript</asp:ListItem>
        <asp:ListItem Value="Asp">Asp</asp:ListItem>
        <asp:ListItem Value="BASIC">BASIC</asp:ListItem>
    </asp:DropDownList>
</div>

回答2:

The 2013 answer is pretty conservative. The select element has the OnChange event, see: this MS doc

The event handler in code-behind is only called after a post event. For Asp controls, you add the AutoPostBack attribute, otherwise you just call the __doPostBack() javascript method.

Complete example:

<select id="select_clients" runat="server" 
   OnServerChange="SelectClients_Change" onchange="__doPostBack()">
</select>

code-behind:

using System.Web.UI.HtmlControls;//HtmlSelect

protected void SelectClients_Change(object sender, EventArgs e)
{
    HtmlSelect HS = sender as HtmlSelect;
    ListItem SelectedItem = HS.Items[HS.SelectedIndex];
}

NB: the options I added dynamically in Page_Load using:

select_clients.Items.Add(new ListItem("...name...", "...value...")

Why use the primitive html elements and __doPostBack call instead of the higher level Asp.Net controls? Well, sometimes this is convenient, e.g. in combination with the Bootstrap framework.

来源：https://stackoverflow.com/questions/19908699/server-event-for-html-select-control

标签

html

events