DropDownList的OnSelectedIndexChanged不会触发

Question

I created these DropDownList s:

<asp:DropDownList CssClass="ComboBoxes" ID="UserComboBox" runat="server" OnSelectedIndexChanged="UserComboBoxSelected"/>
<asp:DropDownList CssClass="ComboBoxes" ID="ShiftComboBox" runat="server"/>

I have this in the code-behind:

protected void UserComboBoxSelected(object sender, EventArgs e)
{
    // ...
}

However, it never fires when I select items in UserComboBox . What am I doing wrong?

Answer 1

You have to set [AutoPostBack][1] to true for firing event on server side code behind file.

<asp:DropDownList CssClass="ComboBoxes" ID="UserComboBox" runat="server" AutoPostBack="true" OnSelectedIndexChanged="UserComboBoxSelected"/>

Gets or sets a value indicating whether a postback to the server automatically occurs when the user changes the list selection, MSDN .

Answer 2

<asp:DropDownList 
    CssClass="ComboBoxes" 
    ID="UserComboBox" 
    runat="server" 
    OnSelectedIndexChanged="UserComboBoxSelected" 
    AutoPostBack="true" />