Extaspnet的页面事件问题

我使用extaspnet开发页面，具体代码如下：
...
<body>
    <form id="form1" runat="server">
    <input type="hidden" id="goUrl" runat="server" />
    <ext:PageManager ID="PageManager1"  FormOffsetRight="5" runat="server" />
    <ext:Form ID="Form2" Width="730" runat="server" ShowHeader="false" LabelWidth="50"
        BodyPadding="5px" EnableBackgroundColor="true" ShowBorder="false" CssClass="xform">
        <Rows>
            <ext:FormRow>
                <Items>
                <ext:DropDownList AutoPostBack="true" OnSelectedIndexChanged="ddlRJZ_SelectedIndexChanged" runat="server" ID="ddlRJZ" ShowLabel="false" Width="168">
                        <ext:ListItem Value="0" Text="AAAA" Selected="true" />
                        <ext:ListItem Value="1" Text="BBBB" />
                        <ext:ListItem Value="2" Text="CCCC" />
            </ext:DropDownList>
           <ext:Button ID="btnSearch" OnClick="btnSearch_Click" runat="server" IconUrl="../ICO/search.png" Text="查詢"></ext:Button>
</Items>
            </ext:FormRow>
        </Rows>
    </ext:Form>
<asp:MultiView ID="MultiView1" runat="server">
        <asp:View ID="View1" runat="server"></asp:View>
        <asp:View ID="View2" runat="server"></asp:View>
        <asp:View ID="View3" runat="server"></asp:View>
</asp:MultiView>.cs:
this.MultiView1.ActiveViewIndex=int.Parse(ddlRJZ.SelectedValue);
我希望选择BBBB，显示View2，可是现在无论怎么选，页面都不显示View2
请教各位这是什么问题，该怎么解决？