问题：
SharePoint 2013上传AI格式文件，再次下载后变成了PS格式文件
需要下载副本才能显示AI格式
解决办法有两个：
第一种，在客户端机器
1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey:
HKEY_CLASSES_ROOT\MIME\Database\Content Type\application/postscript
3. In the right pane, click Extension.
4. On the Edit menu, click Modify.
5. Type .ai, and then press ENTER.
第二种，在服务器端
try adding a .eps mime type to your IIS as application/postscript or image/x-eps. If it already exists as application/postscript or it does not work with that one try changing it to image/x-eps.
