Specify marshalling for P/Invoke string arguments

When you convert from Unicode to ANSI, it is possible that not all Unicode characters can be represented in a specific ANSI code page. *Best-fit mapping* tries to solve this problem by substituting a character for the character that cannot be represented. The use of this feature can cause a potential security vulnerability because you cannot control the character that is chosen. For example, malicious code could intentionally create a Unicode string that contains characters that are not found in a particular code page, which are converted to file system special characters such as '..' or '/'. Note also that security checks for special characters frequently occur before the string is converted to ANSI.

Best-fit mapping is the default for the unmanaged conversion, WChar to MByte. Unless you explicitly disable best-fit mapping, your code might contain an exploitable security vulnerability because of this issue. Code Access Security (CAS) should not be considered a security boundary.

A platform invoke member allows for partially trusted callers, has a string parameter, and does not explicitly marshal the string.

To fix a violation of this rule, explicitly marshal string data types.

Do not suppress a warning from this rule.