在对这个问题进行了大量研究之后，我开始理解并解决了这个问题。
输出缓存不能与 cookie 配合使用的原因
因此，输出缓存不会缓存带有 cookie 的响应的原因是 cookie 可能是用户特定的（例如身份验证、分析跟踪等）。如果一个或多个 cookie 具有属性HttpCookie.Shareable = false，则输出缓存认为响应不可缓存。
包含带有缓存响应的 cookie
这就是棘手的地方。输出缓存将响应标头和内容缓存在一起，并且在将它们发送回用户之前不提供任何挂钩来修改它们。
但是，我编写了以下自定义输出缓存提供程序，以提供在将缓存响应的标头发送回用户之前修改它们的能力（需要 Fasterflect nuget 包）：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Caching;
using System.Web;
using System.Web.Caching;
using Fasterflect;
namespace CustomOutputCache
{
/// <summary>
/// An output cache provider that has ability to modify the http header collection before a cached response is served back to the user.
/// </summary>
public class HeaderModOutputCacheProvider : OutputCacheProvider
{
private static readonly Type OutputCacheEntryType, HttpCachePolicySettingsType;
private static readonly Type[] ParameterTypes;
public static event EventHandler<CachedRequestEventArgs> RequestServedFromCache;
static HeaderModOutputCacheProvider()
{
var systemWeb = typeof(HttpContext).Assembly;
OutputCacheEntryType = systemWeb.GetType("System.Web.Caching.OutputCacheEntry");
HttpCachePolicySettingsType = systemWeb.GetType("System.Web.HttpCachePolicySettings");
ParameterTypes = new[]{
typeof(Guid),
HttpCachePolicySettingsType,
typeof(string),
typeof(string) ,
typeof(string[]),
typeof(int),
typeof(string),
typeof(List<HeaderElement>),
typeof(List<ResponseElement>)
};
}
private readonly ObjectCache _objectCache;
public HeaderModOutputCacheProvider()
{
_objectCache = new MemoryCache("output-cache");
}
#region OutputCacheProvider implementation
public override object Get(string key)
{
var cachedValue = _objectCache.Get(key);
if (cachedValue == null)
return null;
if (cachedValue.GetType() != OutputCacheEntryType)
return cachedValue;
var cloned = CloneOutputCacheEntry(cachedValue);
if (RequestServedFromCache != null)
{
var args = new CachedRequestEventArgs(cloned.HeaderElements);
RequestServedFromCache(this, args);
}
return cloned;
}
public override object Add(string key, object entry, DateTime utcExpiry)
{
_objectCache.Set(key, entry, new CacheItemPolicy { AbsoluteExpiration = utcExpiry });
return entry;
}
public override void Set(string key, object entry, DateTime utcExpiry)
{
_objectCache.Set(key, entry, new CacheItemPolicy { AbsoluteExpiration = utcExpiry });
}
public override void Remove(string key)
{
_objectCache.Remove(key);
}
#endregion
private IOutputCacheEntry CloneOutputCacheEntry(object toClone)
{
var parameterValues = new[]
{
toClone.GetFieldValue("_cachedVaryId", Flags.InstancePrivate),
toClone.GetFieldValue("_settings", Flags.InstancePrivate),
toClone.GetFieldValue("_kernelCacheUrl", Flags.InstancePrivate),
toClone.GetFieldValue("_dependenciesKey", Flags.InstancePrivate),
toClone.GetFieldValue("_dependencies", Flags.InstancePrivate),
toClone.GetFieldValue("_statusCode", Flags.InstancePrivate),
toClone.GetFieldValue("_statusDescription", Flags.InstancePrivate),
CloneHeaders((List<HeaderElement>)toClone.GetFieldValue("_headerElements", Flags.InstancePrivate)),
toClone.GetFieldValue("_responseElements", Flags.InstancePrivate)
};
return (IOutputCacheEntry)OutputCacheEntryType.CreateInstance(
parameterTypes: ParameterTypes,
parameters: parameterValues
);
}
private List<HeaderElement> CloneHeaders(List<HeaderElement> toClone)
{
return new List<HeaderElement>(toClone);
}
}
public class CachedRequestEventArgs : EventArgs
{
public CachedRequestEventArgs(List<HeaderElement> headers)
{
Headers = headers;
}
public List<HeaderElement> Headers { get; private set; }
public void AddCookies(HttpCookieCollection cookies)
{
foreach (var cookie in cookies.AllKeys.Select(c => cookies[c]))
{
//more reflection unpleasantness :(
var header = cookie.CallMethod("GetSetCookieHeader", Flags.InstanceAnyVisibility, HttpContext.Current);
Headers.Add(new HeaderElement((string)header.GetPropertyValue("Name"), (string)header.GetPropertyValue("Value")));
}
}
}
}
你可以这样连接它：
<system.web>
<caching>
<outputCache defaultProvider="HeaderModOutputCacheProvider">
<providers>
<add name="HeaderModOutputCacheProvider" type="CustomOutputCache.HeaderModOutputCacheProvider"/>
</providers>
</outputCache>
</caching>
</system.web>
并且可以像这样使用它来插入cookie：
HeaderModOutputCacheProvider.RequestServedFromCache += RequestServedFromCache;
HeaderModOutputCacheProvider.RequestServedFromCache += (sender, e) =>
{
e.AddCookies(new HttpCookieCollection
{
new HttpCookie("key", "value")
});
};