.NET 8响应压缩迁移问题：HttpResponse无Filter属性报错

将应用从.NET Framework 4.8升级到.NET 8时，在实现输出压缩过滤器时遇到问题。

原.NET Framework 4.8实现代码：

public class CompressAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var encodingsAccepted = filterContext.HttpContext.Request.Headers["Accept-Encoding"];
        if (string.IsNullOrEmpty(encodingsAccepted))
            return;
    
        encodingsAccepted = encodingsAccepted.ToUpperInvariant();
        var response = filterContext.HttpContext.Response;
    
        if (encodingsAccepted.Contains("DEFLATE"))
        {
            response.AppendHeader("Content-encoding", "deflate");
            response.Filter = new DeflateStream(response.Filter, CompressionLevel.Fastest);
    
        }
        else if (encodingsAccepted.Contains("GZIP"))
        {
            response.AppendHeader("Content-encoding", "gzip");
            response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
        }
    }
}

修改后的.NET 8代码：

public class CompressAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var encodingsAccepted = filterContext.HttpContext.Request.Headers.AcceptEncoding.FirstOrDefault()?.ToString();
        if (string.IsNullOrEmpty(encodingsAccepted))
            return;

        encodingsAccepted = encodingsAccepted.ToUpperInvariant();
        var response = filterContext.HttpContext.Response;

        if (encodingsAccepted.Contains("DEFLATE"))
        {
            response.Headers.ContentEncoding = "deflate";
            response.Filter = new DeflateStream(response.Filter, CompressionLevel.Fastest);

        }
        else if (encodingsAccepted.Contains("GZIP"))
        {
            response.Headers.ContentEncoding = "gzip";
            response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
        }
    }
}

报错信息：HttpResponse不包含Filter属性的定义，需实现与原代码相同的功能。

方式一：使用.NET 8内置响应压缩中间件（推荐） #

ASP.NET Core（含.NET 8）已内置响应压缩功能，无需手动实现Filter，直接配置即可：

1. 在Program.cs中添加响应压缩服务：

builder.Services.AddResponseCompression(options =>
{
    options.Providers.Add<GzipCompressionProvider>();
    options.Providers.Add<DeflateCompressionProvider>();
    options.MimeTypes = ResponseCompressionDefaults.MimeTypes.Concat(new[] { "application/json" });
});

// 配置压缩级别
builder.Services.Configure<GzipCompressionProviderOptions>(options =>
{
    options.Level = CompressionLevel.Fastest;
});

builder.Services.Configure<DeflateCompressionProviderOptions>(options =>
{
    options.Level = CompressionLevel.Fastest;
});

2. 启用响应压缩中间件（放在app.UseRouting()之后，app.UseEndpoints()之前）：

app.UseResponseCompression();

该方式会自动根据请求的Accept-Encoding头选择对应压缩方式，与原代码功能一致，且为官方推荐实现。

方式二：自定义ActionFilter实现（替代原Filter逻辑） #

若需保持ActionFilter形式，可通过包装IActionResult实现压缩：

public class CompressAttribute : ActionFilterAttribute
{
    public override void OnResultExecuting(ResultExecutingContext context)
    {
        var encodingsAccepted = context.HttpContext.Request.Headers.AcceptEncoding.FirstOrDefault()?.ToString();
        if (string.IsNullOrEmpty(encodingsAccepted))
            return;

        encodingsAccepted = encodingsAccepted.ToUpperInvariant();
        var response = context.HttpContext.Response;

        if (context.Result is ObjectResult objectResult)
        {
            if (encodingsAccepted.Contains("DEFLATE"))
            {
                response.Headers.ContentEncoding = "deflate";
                context.Result = new CompressedObjectResult(objectResult.Value, CompressionType.Deflate);
            }
            else if (encodingsAccepted.Contains("GZIP"))
            {
                response.Headers.ContentEncoding = "gzip";
                context.Result = new CompressedObjectResult(objectResult.Value, CompressionType.Gzip);
            }
        }
    }

    private class CompressedObjectResult : ObjectResult
    {
        private readonly CompressionType _compressionType;

        public CompressedObjectResult(object value, CompressionType compressionType) : base(value)
        {
            _compressionType = compressionType;
        }

        public override async Task ExecuteResultAsync(ActionContext context)
        {
            var response = context.HttpContext.Response;
            await using var memoryStream = new MemoryStream();
            
            // 先将对象序列化到内存流
            await base.ExecuteResultAsync(new ActionContext(context.HttpContext, context.RouteData, context.ActionDescriptor)
            {
                Result = new ObjectResult(Value) { Formatters = Formatters }
            });
            
            // 重置内存流位置
            memoryStream.Position = 0;
            
            // 应用压缩
            response.ContentLength = null; // 压缩后长度变化，清除原长度
            if (_compressionType == CompressionType.Gzip)
            {
                await using var gzipStream = new GZipStream(response.Body, CompressionLevel.Fastest);
                await memoryStream.CopyToAsync(gzipStream);
            }
            else if (_compressionType == CompressionType.Deflate)
            {
                await using var deflateStream = new DeflateStream(response.Body, CompressionLevel.Fastest);
                await memoryStream.CopyToAsync(deflateStream);
            }
        }
    }

    private enum CompressionType
    {
        Gzip,
        Deflate
    }
}

说明：

• 改用OnResultExecuting方法，在结果执行前替换为自定义压缩结果
• 通过MemoryStream先序列化对象，再通过压缩流写入响应体
• 该方式仅针对ObjectResult（如API返回的JSON结果），若需支持其他类型结果，可扩展对应处理逻辑

内容的提问来源于stack exchange，提问作者Slepoyi