I code below to display files's info in a DataGrid from local drive, it works fine.

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 You should URL sth like this (R is just a mapping drive to your network resource )

\\fileServerName\Directory 

Thank you for help.

Once I changed to "\\order_server\order,  another error occured:

Logon failure: unknown user name or bad password

But, I can mapped \\order_server\order as R and open it without error.

I guess you should logon to the ActiveDirectory sth like

System.DirectoryServices.DirectoryEntry d = new System.DirectoryServices.DirectoryEntry("", "", "", System.DirectoryServices.AuthenticationTypes.None); 

http://www.codeproject.com/KB/system/everythingInAD.aspx 

I added

<identity impersonate="true" />

it works now