升级到 asp.net core 3.1 后声明逐字变量时出错

如何解决升级到 asp.net core 3.1 后声明逐字变量时出错

在将我的 Asp.Net Core MVC Webapp 解决方案从 .Net Core 2.2 迁移到 .Net Core 3.1 后，我遇到了一个奇怪的错误。
我按照官方 docs 中描述的步骤，更新程序、启动、nuget 包...

我正在使用 Syncfusion Essential Studio 2 - 我认为这与此错误无关 - 在许多视图中，我正在声明变量/创建对象，例如创建用于在 Datagrid 中查找的 DropDownList：

@model CultureMultiModel

@{
    var userCultLookupDDL = new Syncfusion.EJ2.DropDowns.DropDownList()
    {
        FilterType = Syncfusion.EJ2.DropDowns.FilterType.Contains,Fields = new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "display",Value = "Name",GroupBy = "Parent" }
        ...
    };
    var userCultParams = new { @params = userCultLookupDDL };

这在 2.2 中运行良好，但现在我在 new { @params ...
上遇到错误 将鼠标悬停在@params 上时，将显示以下内容：
CS1525：无效的表达式术语“参数”
CS1003: 语法错误，',' 预期

我尝试了很多东西：

• 使用圆括号@(params) 给出同样的错误
• 添加 nuget 包 Microsoft.AspNetCore.Mvc.Razor.Extensions，同样的错误
• 在项目文件中添加了 <AddRazorSupportForMvc>true</AddRazorSupportForMvc>，同样的错误
• 更改为@Params 或@arams 会出现错误 CS0103：当前上下文中不存在该名称

由于在编辑 cshtml 文件时立即编译/验证期间发生这种情况，我认为这与启动无关，但为了完整性我还是添加了它：

public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<myContext>(options =>
                options.UsesqlServer(
                    Configuration.GetConnectionString("myConnection"),builder => builder.MigrationsAssembly("myDAL")));


            services.AddDefaultIdentity<IdentityUser>()
                .AddRoles<IdentityRole>()
                .AddRoleManager<RoleManager<IdentityRole>>()
                .AddEntityFrameworkStores<ApplicationDbContext>();
            
            services.AddLocalization(options => options.ResourcesPath = "Resources");
            LocalizationSupport localizationSupport = new LocalizationSupport();
            services.Configure<RequestLocalizationoptions>(options =>
            {
                options.DefaultRequestCulture = new RequestCulture(culture: "en",uiCulture: "en");
                options.SupportedCultures = localizationSupport.SupportedCultures;
                options.SupportedUICultures = localizationSupport.SupportedCultures;
            });

            services.AddMemoryCache();

            services
                .AddMvc()
                .AddViewLocalization()
                .AddDataAnnotationsLocalization(options =>
                {
                    options.DataAnnotationLocalizerProvider = (type,factory) =>
                        factory.Create(typeof(SharedModelLocale));
                })
                .AddNewtonsoftJson(options =>
                {
                    options.SerializerSettings.ContractResolver = new DefaultContractResolver();
                });
            ;

            services
                .AddControllersWithViews()
                .AddNewtonsoftJson(
                    options => options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
                );
            services.AddRazorPages();

            services.Configure<IdentityOptions>(options =>
            ...

            services.AddHttpContextAccessor();
        }

        public void Configure(IApplicationBuilder app,IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            // << Localization           
            LocalizationSupport localizationSupport = new LocalizationSupport();
            var options = new RequestLocalizationoptions
            {
                DefaultRequestCulture = new RequestCulture("en"),SupportedCultures = localizationSupport.SupportedCultures,SupportedUICultures = localizationSupport.SupportedCultures,};
            app.UseRequestLocalization(options);
            // >> Localization
            app.UseStaticFiles();
            app.UseCookiePolicy();

            app.UseRouting();

            app.UseAuthentication();
            app.UseAuthorization();

            app.UseEndpoints(endpoints => {
                endpoints.MapAreaControllerRoute(name: "IdentityRoute",areaName: "Identity",pattern: "{area:exists}/{controller=Home}/{action=Index}");
                endpoints.MapDefaultControllerRoute();
            });
        }

和我的项目文件

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <packagereference Include="markdig" Version="0.22.1" />
    <packagereference Include="Microsoft.AspNetCore.Identity.UI" Version="3.1.15" />
    <packagereference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.1.1" />
    <packagereference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.1.5" PrivateAssets="All" />
    <packagereference Include="Syncfusion.EJ2.AspNet.Core" Version="19.1.0.59" />
    <packagereference Include="System.ServiceModel.Http" Version="4.5.3" />
  </ItemGroup>

这可能是一件微不足道的事情，但在任何文档中都没有提及此事，我的搜索也没有返回任何内容。