public string GetVo4() { var expando = new ExpandoModel(); expando.AddPropertyFilter(ExpandoPropertyFilterFactory.CreateExcludeFilter("bad")); expando.Set("A", () => Task.FromResult("abc")); expando.Set("B", async() => await Task.FromResult("abc")); expando.Set("bad", () => Task.FromResult("bad")); return(JsonConvert.SerializeObject(expando, Formatting.Indented)); }