迁移到 .NET Core 3.1 - 缺少 Newtonsoft

Question

我刚刚从 2.2 迁移到 ASP.NET Core 3.1，我收到了这个错误：

System.NotSupportedException: The collection type 'System.Collections.Generic.Dictionary`2[System.Object,System.Object]' is not supported.
   at System.Text.Json.JsonClassInfo.GetElementType(Type propertyType, Type parentType, MemberInfo memberInfo, JsonSerializerOptions options)
   at System.Text.Json.JsonClassInfo.CreateProperty(Type declaredPropertyType, Type runtimePropertyType, Type implementedPropertyType, PropertyInfo propertyInfo, Type parentClassType, JsonConverter converter, JsonSerializerOptions options)
   at System.Text.Json.JsonClassInfo.AddProperty(Type propertyType, PropertyInfo propertyInfo, Type classType, JsonSerializerOptions options)
   at System.Text.Json.JsonClassInfo.AddPolicyProperty(Type propertyType, JsonSerializerOptions options)
   at System.Text.Json.JsonClassInfo..ctor(Type type, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializerOptions.GetOrAddClass(Type classType)
   at System.Text.Json.WriteStackFrame.Initialize(Type type, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializer.WriteAsyncCore(Stream utf8Json, Object value, Type inputType, JsonSerializerOptions options, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
   at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)

但是，我安装了这个包Microsoft.AspNetCore.Mvc.NewtonsoftJson，还在启动中添加了services.AddControllers().AddNewtonsoftJson()

那么为什么仍然忽略 Newtonsoft 而使用 System.Text.Json 呢？

编辑： 代码抛出错误：

public async Task<Dictionary<object, object>> GetTemplatesDictAsync(
           int? from = 0,
            int? take = 100,
            string search = null)
        {
            var _templates = await _repository.GetAllAsync(from, take, search, );

            var _dict = _templates.ToDictionary(t => (object)t.id, t => (object)t);

            // also append a property with original list
            _dict.Add("list", _templates);

            return _dict;
        }

注意：我将 Dictionary<object, object> 更改为 Dictionary<string, object> 并且代码有效。不过，问题是为什么不使用 Newtonsoft.Json。

EDIT2：

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddAuthentications(Configuration);
            services.AddAutoMapping();
            services.AddMemoryCache();
            services.AddOData();

            // 3.1:
            services.AddControllers()
                        .AddNewtonsoftJson()
                    ;

           // used in 2.2:
           // var mvcCoreBuilder = services.AddMvcCore();
            // mvcCoreBuilder
            //     .AddFormatterMappings()
            //     .AddJsonFormatters()

谢谢

Answer 1

在 .NET Core 3+ 项目中，您有一组不同的调用来替换 MVC。所以你可能会有以下之一：

services.AddControllers().AddNewtonsoftJson();
services.AddControllersWithViews().AddNewtonsoftJson();
services.AddRazorPages().AddNewtonsoftJson();

如果这不起作用，请告诉我们更多您在哪里使用它。

您可以在here 找到更详细的方法。它对我有用。