asp.net core 3 WebApi System.Text.Json 返回数据配置

一、System.Text.Json

引用：

using System.Text.Encodings.Web;
using System.Text.Json;
using System.Text.Unicode;
 

　　

  services.AddJsonOptions(options =>
            {
                //格式化日期时间格式
                options.JsonSerializerOptions.Converters.Add(new DatetimeJsonConverter());
                //数据格式首字母小写
                //options.JsonSerializerOptions.PropertyNamingPolicy =JsonNamingPolicy.CamelCase;
                //数据格式原样输出
                options.JsonSerializerOptions.PropertyNamingPolicy = null;
                //取消Unicode编码
                options.JsonSerializerOptions.Encoder = JavaScriptEncoder.Create(UnicodeRanges.All);
                //忽略空值
                options.JsonSerializerOptions.IgnoreNullValues = true;
                //允许额外符号
                options.JsonSerializerOptions.AllowTrailingCommas = true;
                //反序列化过程中属性名称是否使用不区分大小写的比较
                options.JsonSerializerOptions.PropertyNameCaseInsensitive = false;
            });

　　扩展：

using System;
using System.Text.Json;
using System.Text.Json.Serialization;


public class DatetimeJsonConverter : JsonConverter<DateTime>
    {
        public override DateTime Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            if (reader.TokenType == JsonTokenType.String)
            {
                if (DateTime.TryParse(reader.GetString(), out DateTime date))
                    return date;
            }
            return reader.GetDateTime();
        }

        public override void Write(Utf8JsonWriter writer, DateTime value, JsonSerializerOptions options)
        {
            writer.WriteStringValue(value.ToString("yyyy-MM-dd HH:mm:ss"));
        }
    }

　　二、Newtonsoft.Json

1. Install-Package Microsoft.AspNetCore.Mvc.NewtonsoftJson -Version 3.1.0
2. startup配置代码如下： 

3. 引用：
   

   using Newtonsoft.Json;
   using Newtonsoft.Json.Serialization;
   

   　　

   services.AddNewtonsoftJson(options =>
               {
                   //设置时间格式
                   options.SerializerSettings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
                   //忽略循环引用
                   options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
                   //数据格式首字母小写
                   //options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
                   //数据格式按原样输出
                   options.SerializerSettings.ContractResolver = new DefaultContractResolver();
                   //忽略空值
                   options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;
               });