输出页没有正确呈现

我创建了一个带有一些控件的页面。当我输入<% label。Text = "changed";%>"，则在页面执行后不呈现Label的文本值。为什么?

<div>
   <tagprefix:MD ID="CC"  runat="server" />
        <asp:TextBox runat="server"  ID="TextBox1"/>
        <asp:Button Text="button" ID="Button"  runat="server" onclick="Button_Click" />
        <%= "Hello..." %>
        <% label.Text = "changed"; %>                          //working fine
        <asp:Label ID="label" Text="text" runat="server" />
        <% label.Text = "changed"; %>               // do not work
</div>

string hello = "hello";
Response.Write( hello );
hello = "world"