Local Report in visual studio 2017 Shows Error in Value field

Question

Local Report Rdlc in vs2017 when try to make expression in field it gives #error but it works in other machine without issue

I'm just making simple report and make group in one column, when try to run report in my new computer report shows #error in fields that i made any expression on it even if concatenation

but if move the report file in my old machine it works fine

this is example of expression i used =Fields!CollegeNameEn.Value & "tt" it not shows in report

I expected to show value but it shows #error

Answer 1

after searching I found this post with similar issue

https://forums.asp.net/t/1757832.aspx?Reportviewer+2010+showing+Error+for+expressions

and puting these lines in code fixed my issue

var sec = new System.Security.PermissionSet(System.Security.Permissions.PermissionState.Unrestricted); localReport.SetBasePermissionsForSandboxAppDomain(sec);

I don't why I need these lines but issue is fixed ho[e this will help anyone have the issue