DefaultHttpRequest 已从 public 更改为 internal 作为 ASP 的一部分.NET Core 3.0 版本，这意味着它不再可用.在您显示的代码中，似乎没有任何理由创建或依赖 DefaultHttpRequest.

DefaultHttpRequest was changed from public to internal as part of the ASP.NET Core 3.0 release, which means it's no longer available. In the code you've shown, there doesn't appear to be any reason to create or depend on DefaultHttpRequest.

我建议将代码更改为如下所示:

I recommend changing the code to something like this:

private static async Task<UserInfo> Upload(byte[] buffer, FormFileCollection formFileCollection,
    HttpRequest httpRequest, Dictionary<string, StringValues> dictionary)
{
    // ...

    httpRequest.Form = new FormCollection(dictionary, formFileCollection);

    // Update all other references to defaultHttpRequest

    // ...
}

public async void Test1Up() // async void is generally bad, but that's a separate issue
{ 
    // ...

    var httpContext = new DefaultHttpContext(featureCollection);
    var httpRequest = httpContext.Request;

    // Update all other references to defaultHttpContext and defaultHttpRequest

    // ...
}

不要传递DefaultHttpRequest，而是使用抽象的HttpRequest.在 Upload 中设置的 Form 属性是 HttpRequest 的一部分，因此应该按原样工作.也无需创建DefaultHttpRequest 的实例:DefaultHttpContext 构造函数为您完成此操作并通过其Request提供它代码> 属性.

Rather than passing around DefaultHttpRequest, use the abstract HttpRequest. The Form property being set in Upload is part of HttpRequest, so that should work as-is. There's also no need to create an instance of DefaultHttpRequest: the DefaultHttpContext constructor does this for you and provides it via its Request property.

这是官方公告和相关的链接问题.