在.Net核心中，如何从HttpContext中设置控制器中的变量以在所有控制器方法中使用？

public static class SharedContext
{
    public static string MyVariable { get; set; }
}

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<SharedContext>();
    services.AddControllers();
}

public class SetSharedVariableMiddleware
{
    private readonly RequestDelegate _next;

    public SetSharedVariableMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        // 假设我们从某个地方获取变量值
        string value = "SomeValue"; 
        SharedContext.MyVariable = value;

        await _next(context);
    }
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.UseRouting();

    app.UseMiddleware<SetSharedVariableMiddleware>();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

public class MyController : ControllerBase
{
    public IActionResult Index()
    {
        string variable = SharedContext.MyVariable;
        return Ok(variable);
    }
}

public class MyHttpContextFeature : IHttpContextFeature
{
    private readonly HttpContext _httpContext;

    public MyHttpContextFeature(HttpContext httpContext)
    {
        _httpContext = httpContext;
    }

    public HttpContext HttpContext => _httpContext;
}

public void ConfigureServices(IServiceCollection services)
{
    services.AddHttpContextAccessor();
    services.AddControllers(options =>
    {
        options.Filters.Add(new MyHttpContextFeatureAttribute());
    });
}

public abstract class BaseController : ControllerBase
{
    protected string MyVariable => HttpContext.Features.Get<MyHttpContextFeature>()?.HttpContext.Items["MyVariable"] as string;
}

public class MyController : BaseController
{
    public IActionResult Index()
    {
        string variable = MyVariable;
        return Ok(variable);
    }
}

public class SetSharedVariableMiddleware
{
    private readonly RequestDelegate _next;

    public SetSharedVariableMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        // 设置变量
        context.Items["MyVariable"] = "SomeValue";

        await _next(context);
    }
}