replace error

Hi in sample.aspx, I have the below code,
I want to replace blank with "-" and replace with / to "-"
  <% dim sp as string%>   <% sp = Replace(Eval("Name"), " ", "-")%>    <% sp = Replace(sp, "/", "-")%>        <a href='/store/<%=sp %>/<%# Eval("Id") %>'>  
Error is on the aove statement the erors says BC30451: 'sp' is not declared. It may be inaccessible due to its protection level.

Thanks
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