HttpContext.Current在ASP.NET Core中已经不存在了，但是有一个新的
IHttpContextAccessor东西可以注入到您的依赖中并用来检索当前的HttpContext：

public class MyComponent : IMyComponent
{
    private readonly IHttpContextAccessor _contextAccessor;

    public MyComponent(IHttpContextAccessor contextAccessor)
    {
        _contextAccessor = contextAccessor;
    }

    public string GetDataFromSession()
    {
        return _contextAccessor.HttpContext.Session.GetString(*KEY*);
    }
}