public async Task <ITypeParserResult <T?> > ParseAsync(string value, IParameter parameter, CommandContext context) { if (string.IsNullOrWhiteSpace(value)) { return(new NullableTypeParserResult <T>()); } else { var result = await _nonNullableTypeParser.ParseAsync(value, parameter, context); return(NullableTypeParserResult <T> .FromResult(result)); } }