The ITypeConverter interface has been changed to have a \"TDestination Convert(ResolutionContext context)\" instead of \"TDestination Convert(TSource source)\" for the Convert m
You'll have to grab the decimal from the ResolutionContext.SourceValue property:
ResolutionContext.SourceValue
public int? Convert(ResolutionContext context) { var d = (decimal)context.SourceValue; if (d == 0) { return null; } return (int) d; }