How to Accept Files With Specified content type accross the Operating system

as i am trying to upload a File, and i am trying to check for their extension, as i know it is not a good practice, so this is the code which i am doing this. it works fine, but as i am facing issue in Apple Mac Users, they are not unable to upload pdf files.

   if (upload1.HasFile)
      {
       Finfo = new FileInfo(upload1.PostedFile.FileName);
       if (Finfo.Extension.ToLower() == ".docx" || Finfo.Extension.ToLower() == ".doc" || Finfo.Extension.ToLower() == ".xls" ||
                            Finfo.Extension.ToLower() == ".xlsx" || Finfo.Extension.ToLower() == ".pdf" || Finfo.Extension.ToLower() == ".jpg" ||
                            Finfo.Extension.ToLower() == ".png" || Finfo.Extension.ToLower() == ".gif" || Finfo.Extension.ToLower() == ".txt" ||
                            Finfo.Extension.ToLower() == ".mp4" || Finfo.Extension.ToLower() == "ppt" || Finfo.Extension.ToLower() == ".bmp" ||
                            Finfo.Extension.ToLower() == ".swf" || Finfo.Extension.ToLower() == ".rm" || Finfo.Extension.ToLower() == ".pptx")
        {
           // Accept File 
        }
}

now what i thought i will use this code, so that it will solve the problem

if (
        upload1.PostedFile.ContentType == "text/rtf" ||
        upload1.PostedFile.ContentType == "application/doc" ||
        upload1.PostedFile.ContentType == "appl/text" ||
        upload1.PostedFile.ContentType == "application/vnd.msword" ||
        upload1.PostedFile.ContentType == "application/vnd.ms-word" ||
        upload1.PostedFile.ContentType == "application/winword" ||
        upload1.PostedFile.ContentType == "application/word" ||
        upload1.PostedFile.ContentType == "application/msword" ||       
        upload1.PostedFile.ContentType == "application/x-msw6" ||
        upload1.PostedFile.ContentType == "application/x-msword" ||
        upload1.PostedFile.ContentType == "application/pdf" ||
                        FileUpload1.PostedFile.ContentType == "application/x-pdf" ||
        upload1.PostedFile.ContentType == "application/vnd.openxmlformats-officedocument.wordprocessingml.document" ||
        upload1.PostedFile.ContentType == "application/vnd.openxmlformats-officedocument.wordprocessingml.template"
        )

is it good way to Accept Files from users. I need to allow All Files Except EXE,DMG, DLL,CS, SQL, BAT, . how do i ensure that it will work on all operating systems.

Apple user may use OpenOffice, or some other softwares to upload. so we need to allow this type of file also

can anybody tell me how to handle this situations

Solution

i Used File Extension and Even the COntent type validation. along with we restricted user not to upload other than office documents, Even we are tried Telerik Upload controls to achieve the functionalty . once again thank you for all who gave answers .