Compiler Warning (level 1) CS1645

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

The feature you are using is not part of the ISO standard. Code using this feature may not compile on other compilers.

// CS1645.cs
// compile with: /W:1 /t:module /langversion:ISO-1
[assembly:System.CLSCompliant(false)]
// To suppress the warning use the switch: /nowarn:1645
[module:System.CLSCompliant(false)]   // CS1645
class Test
{
}