We recommend using Visual Studio 2017
This documentation is archived and is not being maintained.

Compiler Error CS1644

Feature 'feature' is not part of the standardized ISO C# language specification, and may not be accepted by other compilers

This error occurs if you specified the /langversion option ISO-1 and the code you are compiling uses features that are not part of the ISO 1.0 standard. To resolve this error, do not use any of the C# 2.0 compiler features such as generics or anonymous methods with the ISO-1 compatibility option.

The following sample generates CS1644:

// CS1644.cs
// compile with: /langversion:ISO-1 /target:library
class C<T> {}   // CS1644