The DotNetNuke.Web.Mvp.ModuleViewBase sets a property called ‘AutoDataBind = true’.  As a result the DataBind() method for the page is always called in the Page_PreRenderComplete event. 

If you use the following familiar snippet of code you find that your controls will be data bound twice.  Once when your code calls DataBind() and a second time when it is called during the Page_PreRenderComplete event.

ddlStatus.DataSource = Model.StatusList;
ddlStatus.DataBind();

Here is an example of how to properly bind a DropDownList for an MVP based module.

<asp:DropDownList ID="ddlStatus" runat="server"
    DataSource='<%#Model.StatusList%>'
    DataTextField="Description"
    DataValueField="Id"    SelectedValue='<%#Model.Post.PostStatus %>'>
</asp:DropDownList>

It is important to point out again that you should not call ddlStatus.DataBind() from the code behind.  Calling this is a waste because the AutoDataBind property is going to force everything to rebind again during Page_PreRenderComplete.