startup.cs
services.AddControllers(setup => {setup.ReturnHttpNotAcceptable = true;//默认false:返回默认格式，不返回406setup.OutputFormatters.Add(new XmlDataContractSerializerOutputFormatter());//add添加在序列后//默认格式,序列首项下标未0即默认//setup.OutputFormatters.Insert(0, new XmlDataContractSerializerOutputFormatter()); });