/langversion (Conformant Syntax) (C# Compiler Options)
Causes the compiler to only accept syntax that is included in the ISO/IEC 23270:2003 C# language specification.
Version 1.0 of the C# specification represents the functionality available with /langversion:ISO-1. The Visual Studio Developer Center contains all specifications as Microsoft Word files. The ISO/IEC 23270:2006 specification is available at http://standards.iso.org/ittf/PubliclyAvailableStandards/c042926_ISO_IEC_23270_2006(E).zip.
Metadata referenced by your C# application is not subject to /langversion compiler option.
Because each version of the C# compiler contains extensions to the language specification, /langversion does not give you the equivalent functionality of an earlier version of the compiler.
Regardless of which /langversion setting you use, you will use the current version of the common language runtime to create your .exe or .dll. One exception is friend assemblies and /moduleassemblyname (Specify Friend Assembly for Module) (C# Compiler Option), which work under /langversion:ISO-1.
To set this compiler option in the Visual Studio development environment
Open the project's Properties page. For details, see How to: Set Build Properties (C#).
Click the Build property page.
Click the Advanced button.
Modify the Language Version property.
For information about how to set this compiler option programmatically, see LanguageVersion.