Security transparent assemblies should not contain security critical code

This warning is supported in the stand-alone version of FxCop only. It is not supported in Code Analysis, which is integrated into Visual Studio.

Cause

Critical code cannot occur in a 100% transparent assembly.

Rule Description

This rule analyzes 100% transparent assemblies for any SecurityCritical annotations at the type, field, and method level. This rule is helpful because it flags code that exists in a 100% transparent assembly. Code in a 100% transparent assembly triggers either a security exception or unexpected behavior at run time.

The .NET Framework 2.0 introduced a feature named transparency. Individual methods, fields, interfaces, classes, and types can be either transparent or critical.

Transparent code is not allowed to elevate security privileges. Therefore, any permissions that are granted or demanded of it are automatically passed through the code to the caller or host AppDomain. Examples of 'elevations' include Asserts, LinkDemands, SuppressUnmanagedCode, and 'unsafe' code.

An assembly can be either 100% transparent, 100% critical, or mixed transparent/critical.

To mark an assembly as 100% transparent, add the assembly-level attribute:

 [assembly:System.Security.SecurityTransparent]

To mark an assembly as 100% critical, add the assembly-level attribute:

[assembly:System.Security.SecurityCritical(System.Security.SecurityCriticalScope.Everything)]

To mark an assembly as mixed transparent/critical, add the assembly-level attribute:

 [assembly:System.Security.SecurityCritical]

Transparent code cannot occur in a 100% critical assembly, and critical code cannot occur in a 100% transparent assembly.

How to Fix Violations

To resolve the issue, either mark the assembly as mixed transparent/critical, or remove the SecurityCritical attribute from the flagged code.

When to Exclude Warnings

Do not exclude a message from this rule.

Example