But i get error:- Invalid URI: There is an invalid sequence in the string. "
What could be the problem!!!

The citname normally returns a string with a space
for example "need help"

CitName=" & DataBinder.Eval(Container.DataItem, "mcatid") &

but if i bind it to an integer e.g mcatid as above it doesn't return the error
i have used ToString() also used replace function still no luck
Also constructed the hyperlink in codebehind no LUCK

<asp:HyperLink id="Hyperlink1" Cssclass="MenuUnselected" Text='<%# DataBinder.Eval(Container.DataItem, "cat_cities")%>' NavigateUrl='<%# "../Showcrete.aspx?CategoryID=" & DataBinder.Eval(Container.DataItem, "mcatid") & "&CitName=" & DataBinder.Eval(Container.DataItem, "mcatid") & "&s=" & Container.ItemIndex.ToString() %>' runat="server" />