确保在aspx中将DropDownList的AutoPostBack属性设置为True

make sure you set AutoPostBack Property of DropDownList to True in aspx

<asp:dropdownlist id="ddlCompany" runat="server" onselectedindexchanged="ddlCompany_SelectedIndexChanged" autopostback="true" xmlns:asp="#unknown" />

以下是您背后的代码中的事件处理程序

the below is your event handler in code behind

protected void ddlCompany_SelectedIndexChanged(object sender, EventArgs e)
{
   string strCompID = ddlCompany.SelectedValue.ToString();
   //bind here your DetailView's data bsed on the selected ID strCompID.
}