reporting services - ssrs System.IO.File.Exists works well on local but not working on server -

i have sql reporting (ssrs). image, use system.io.file.exists check if file (unc path) exists or not. works on local after upload server, return false.

any suggestion?

i figured out need change report_expressions_default_permissions on server side.

problem solved

see https://social.msdn.microsoft.com/forums/sqlserver/en-us/8ab26a11-af38-44f1-9010-b4f8354a4e14/systemiofileexists-not-working?forum=sqlreportingservices