用正则表达式验证控件过滤fileupload控件上传文件类型收藏

  <asp:RegularExpressionValidator   ID="RegularExpressionValidator1"   runat="server"   ControlToValidate="FileUpload1"  
              ErrorMessage="必须是   jpg或者gif文件"   ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))+(.jpg|.Jpg|.gif|.Gif)$"></asp:RegularExpressionValidator>