索引更改时不会触发 SelectedIndexChanged 事件

Question

我在 asp.net

中有以下 dropdownList 控件

<asp:dropdownlist id="ddlMerchantCity" runat="server"></asp:dropdownlist>

我想在其 SelectedIndexChanged 事件上调用一个方法，但它不会进入 SelectedIndexChanged 事件的主体。我的代码有什么问题？

Protected Sub ddlMerchantCity_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ddlMerchantCity.SelectedIndexChanged
            Response.Write("<script>alert('from selectindex')</script>")
            LoadMerchant()
        End Sub

编辑：即使在 asp.net 下拉列表中添加 OnSelectedIndexChanged 也不起作用

<asp:dropdownlist id="ddlMerchantCity" runat="server" OnSelectedIndexChanged="ddlMerchantCity_SelectedIndexChanged"></asp:dropdownlist>

Answer 1

当这个事件发生时，编译器不知道你有一个方法来做某事。您可以通过在 aspx 标记中定义它来调用此方法：

<asp:dropdownlist id="ddlMerchantCity" runat="server" OnSelectedIndexChanged="ddlMerchantCity_SelectedIndexChanged" AutoPostBack="true"></asp:dropdownlist>

或者你可以在后面的代码中设置：

AddHandler ddlMerchantCity.SelectedIndexChanged, AddressOf Me.ddlMerchantcity_SelectedIndexChanged

不过我宁愿通过标记来完成。更快更容易。

/编辑：如果添加 OnSelectedIndexChanged 没有帮助，您可能必须设置 AutoPostback="true"

要在 AutoPostBack 描述中引用 MSDN：

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

索引更改时不会触发 SelectedIndexChanged 事件

SelectedIndexChanged event does not get fired on Index change

asp.net

vb.net

cascadingdropdown

selectedindexchanged