+.I \-langversion:TEXT
+The option specifies the version of the language to use. The feature
+set is different in each C# version. This switch can be used to force
+the compiler to allow only a subset of the features.
+The possible values are:
+.nf
+
+Default - Instruct compiler to use the latest version. Equivalent
+is to omit the switch.
+
+ISO-1 - Restrict compiler to use only ISO standardized features.
+The usage of features such as generics, static classes, anonymous
+methods will lead to error.
+.TP