Unable to create assembly for DirectoryServices (v4.0) in Sql Server 2012 by natalie1234567

When trying to create an assembly reference for DirectoryServices using sql commands, I get an error (db trustworthy parameter is set and EXTERNAL ACCESS/UNSAFE assembly permissions have been granted to user)

CREATE ASSEMBLY [System.DirectoryServices]
FROM 'C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\System.DirectoryServices.dll'
WITH PERMISSION_SET = UNSAFE
GO

Error:
Warning: The Microsoft .NET Framework assembly 'system.directoryservices, version=4.0.0.0, culture=neutral, publickeytoken=b03f5f7f11d50a3a.' you are registering is not fully tested in the SQL Server hosted environment and is not supported. In the future, if you upgrade or service this assembly or the .NET Framework, your CLR integration routine may stop working. Please refer SQL Server Books Online for more details.
Msg 6218, Level 16, State 2, Line 3
CREATE ASSEMBLY for assembly 'System.DirectoryServices' failed because assembly 'System.DirectoryServices' failed verification. Check if the referenced assemblies are up-to-date and trusted (for external_access or unsafe) to execute in the database. CLR Verifier error messages if any will follow this message
[ : System.DirectoryServices.ActiveDirectorySecurity::PurgeAccessRules][mdToken=0x6000009][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::PurgeAuditRules][mdToken=0x6000010][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::get_AccessRightType][mdToken=0x6000015][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::get_AccessRuleType][mdToken=0x6000016][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::get_AuditRuleType][mdToken=0x6000017][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::ModifyAccessRule][mdToken=0x6000008][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::ModifyAuditRule][mdToken=0x600000f][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::AccessRuleFactory][mdToken=0x6000011][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::AuditRuleFactory][mdToken=0x6000013][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::AccessRuleFactory][mdToken=0x6000012][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::AuditRuleFactory][mdToken=0x6000014][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::.ctor][mdToken=0x6000001][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurity::AddAccessRule][mdToken=0x6000002][offset 0x00000000] Code size is zero.
[ : System.DirectoryServices.ActiveDirectorySecurit...