我正在尝试从 ddlMake 下拉列表中触发 SelectedIndexChanged，但该事件未触发，如果我将 ddlMake 移到 CreateUserWizard 之外，它将起作用。我做错什么了吗：
<asp:CreateUserWizard runat="server" ID="RegisterUser" ViewStateMode="Disabled" OnCreatingUser="RegisterUser_CreatingUser" OnCreatedUser="RegisterUser_CreatedUser" >
<LayoutTemplate>
<asp:PlaceHolder runat="server" ID="wizardStepPlaceholder" />
<asp:PlaceHolder runat="server" ID="navigationPlaceholder" />
</LayoutTemplate>
<WizardSteps>
<asp:CreateUserWizardStep runat="server" ID="CreateUserWizardStep1">
<ContentTemplate>
<p class="message-info">
Passwords are required to be a minimum of <%: Membership.MinRequiredPasswordLength %> characters in length.
</p>
<p class="validation-summary-errors">
<asp:Literal runat="server" ID="ErrorMessage" />
</p>
<div class="row-fluid MT35">
<div class="span3">User ID:</div>
<div class="span8">
<asp:TextBox runat="server" ID="UserName" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="UserName"
CssClass="field-validation-error"
ErrorMessage="The user name field is required." Display="Dynamic" />
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" Text="Username length must be between 5 to 12 characters without spacing."
ControlToValidate="UserName" SetFocusOnError="true"
ValidationExpression="^[a-zA-Z0-9'@&#_]{5,12}$" Display="Dynamic" />
</div>
<div class="row-fluid ">
<div class="span3">Password:</div>
<div class="span8">
<asp:TextBox runat="server" ID="Password" TextMode="Password" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="Password"
CssClass="field-validation-error" ErrorMessage="The password field is required." />
</div>
<div class="row-fluid ">
<div class="span3">Confirm Password:</div>
<div class="span8">
<asp:TextBox runat="server" ID="ConfirmPassword" TextMode="Password" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ControlToValidate="ConfirmPassword"
CssClass="field-validation-error" Display="Dynamic" ErrorMessage="The confirm password field is required." />
<asp:CompareValidator ID="CompareValidator1" runat="server" ControlToCompare="Password" ControlToValidate="ConfirmPassword"
CssClass="field-validation-error" Display="Dynamic" ErrorMessage="The password and confirmation password do not match." />
</div>
</div>
<div class="row-fluid MT35">
<div class="span3">Your Car:</div>
<div class="span8 YourCarInformation">
<asp:DropDownList ID="ddlCarMake" OnSelectedIndexChanged="ddlMake_SelectedIndexChanged" AutoPostBack="True" runat="server" CssClass="span12"></asp:DropDownList>
<asp:DropDownList ID="ddlCarModel" runat="server" CssClass="span12"></asp:DropDownList>
<asp:TextBox ID="txtRegistration" CssClass="pull-left" runat="server" placeholder="registration date dd/mm/yyyy"></asp:TextBox>
</div>
</div>
</div>
<div class="row-fluid">
<div class="span3">Recieve Newsletter:</div>
<div class="span8 RadioBtn">
<label class="radio">
<asp:RadioButtonList ID="rbNewsLetter" runat="server" RepeatDirection="Horizontal">
<asp:ListItem Text="Yes" Value="true" Selected="True" />
<asp:ListItem Text="No" Value="false" />
</asp:RadioButtonList>
</label>
</div>
</div>
</div>
</div>
</ContentTemplate>
<CustomNavigationTemplate />
</asp:CreateUserWizardStep>
</WizardSteps>
</asp:CreateUserWizard>
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
RegisterUser.ContinueDestinationPageUrl = Request.QueryString["ReturnUrl"];
DropDownList ddlCarMake =
(DropDownList)CreateUserWizardStep1.ContentTemplateContainer.FindControl("ddlCarMake");
DropDownList ddlCarModel =
(DropDownList)CreateUserWizardStep1.ContentTemplateContainer.FindControl("ddlCarModel");
ddlCarMake.DataSource = ds.Tables[0];
ddlCarMake.DataTextField = "CarMake";
ddlCarMake.DataValueField = "CarMake";
ddlCarMake.DataBind();
ddlCarMake.Items.Insert(0, new ListItem("Any", ""));
ddlCarMake.Items.Insert(ds.Tables[0].Rows.Count + 1, new ListItem("Others", "Others"));
ddlCarModel.Items.Insert(0, new ListItem("Any", ""));
}
}
protected void ddlMake_SelectedIndexChanged(object sender, EventArgs e)
{
VehicleBLL vehicleBll = new VehicleBLL();
DropDownList ddlCarMake = (DropDownList)CreateUserWizardStep1.ContentTemplateContainer.FindControl("ddlCarMake");
DropDownList ddlCarModel = (DropDownList)CreateUserWizardStep1.ContentTemplateContainer.FindControl("ddlCarModel");
DataSet ds = null;
if (ddlCarMake.SelectedIndex != 0)
{
ds = vehicleBll.GetCarModel(ddlCarMake.SelectedValue);
ddlCarModel.DataSource = ds.Tables[0];
ddlCarModel.DataTextField = "CarModel";
ddlCarModel.DataValueField = "CarModel";
ddlCarModel.DataBind();
ddlCarModel.Items.Insert(0, new ListItem("Any", ""));
}
}