在 .NET Core 3.1 中阅读 RSS 不起作用

Question

我有非常简单的 .NET Core Web Api 代码，以前可以在 .NET Core 2.2 中运行，但在升级到 3.1 后停止运行

[HttpGet]
[Route("api/news")]
public IEnumerable<SyndicationItem> GetNews(string source)
{
    var feed = SyndicationFeed.Load(XmlReader.Create(source));
    return feed.Items;
}

我可以通过导航到以下位置来调用它：https://localhost:5001/api/news?source=http://feeds.bbci.co.uk/news/rss.xml

在调试中我可以看到它很好地获取了项目，但是抛出这个错误返回它们，我不明白为什么它在我升级到 3.1 后停止工作以及如何修复它

请指教，谢谢！

System.NotSupportedException: The collection type 'System.Collections.Generic.Dictionary`2[System.Xml.XmlQualifiedName,System.String]' on 'System.ServiceModel.Syndication.SyndicationItem.AttributeExtensions' 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..ctor(Type type, JsonSerializerOptions options) at System.Text.Json.JsonSerializerOptions.GetOrAddClass(Type classType) at System.Text.Json.JsonClassInfo.get_ElementClassInfo() at System.Text.Json.JsonSerializer.Write(Utf8JsonWriter writer, Int32 originalWriterDepth, Int32 flushThreshold, JsonSerializerOptions options, WriteStack& state) 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) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|29_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync() --- End of stack trace from previous location where exception was thrown --- at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope) at Microsoft.AspNetCore.Routing.EndpointMiddleware.g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger) at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Answer 1

.NET Core 3.x 中的默认 JSON 序列化程序更改为 System.Text.Json。在这种情况下，您可能需要指定使用 Newtonsoft.Json 作为默认序列化器（旧版本 .NET Core 中的默认序列化器）。

在Startup.cs中：

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers().AddNewtonsoftJson();

    // other settings in ConfigureServices...
}

在 .NET Core 3.1 中阅读 RSS 不起作用

Reading RSS in .NET Core 3.1 is not working

rss

syndication-feed

.net-core