C# AND vb issue

Hi i have a c# web project which is working fine, i need to use a usercontrol which has been written in vb. i am refferencing the control like this..
<%@ Register TagPrefix="ucEktron" TagName="Editor" Src="/controls/Editor/ContentDesignerControl.ascx" %>
<ucEktron:Editor ID="contentEditor" runat="server" />


But i am getting this error when trying to build
Error    25    The type or namespace name 'controls_Editor_ContentDesignerControl' does not exist in the namespace 'NFU_Custom_Cms' (are you missing an assembly reference?)    C:\development\NFU_Websites\NFU_Custom_Cms\CompetitionItem.aspx.designer.cs    320    42    NFU_Custom_Cms
the vb file does not include a namespace, any ideas how i can get around this???
many thanks

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