To add a triple-slash XML documentation summary to a generated class, struct, interface, enum, attribute, field, property or method, use:

BuildableExpression.SourceCode(sc =>
{
    sc.AddClass("MyClass", cls =>
    {
        cls.SetSummary(
            "This is my generated class, " + 
            "and it's pretty special");
    });
});

File Headers

To add a file header to a generated c# source code file, use:

BuildableExpression.SourceCode(sc =>
{
    sc.SetHeader($@"
// - - - - - - - - - - - - - - - - - - - - -
// This is generated code.
// Generated on: {DateTime.Now}
// Don't change this file directly, as your
// changes may be overwritten.
// - - - - - - - - - - - - - - - - - - - - -");
});