because your sql has "<" and ">", use <![CDATA[]]>
<dynamic prepend="WHERE"> <isNotEqual prepend="AND" property="DataInicio" compareValue="1/1/0001 12:00:00 AM"> <![CDATA[a.dat_inicio >= #DataInicio#]]> </isNotEqual> <isNotEqual prepend="AND" property="DataFim" compareValue="1/1/0001 12:00:00 AM"> <![CDATA[a.dat_fim <= #DataFim#]]> </isNotEqual>

