AspNet Core2 浏览器缓存使用

Core2中使用Microsoft.AspNetCore.Mvc下的ResponseCacheAttribute特性来控制Http Get请求的缓存

原理是设置http请求 响应头的Cache-control来告诉浏览器如何进行客户端缓存

1、在Startup的ConfigureServices方法里面设置一个CacheProfiles,Duration属性定义浏览器缓存的秒数，CacheProfiles一个通用的缓存配置项

 services.AddMvc(option =>
            {
                /*客户端缓存*/
                option.CacheProfiles.Add("default", new Microsoft.AspNetCore.Mvc.CacheProfile
                {
                    Duration = 600 /*10分钟*/
                });
            });

2、在需要缓存的Action上面添加ResponseCacheAttribute特性，CacheProfileName 的值使用服务配置的名称，该Action将使用配置项进行缓存

[ResponseCache(CacheProfileName = "default")]

也可以在Action 上赋予 Duration 值，指定浏览器缓存的时间  

 查看ResponseCacheAttribute中的代码

    public unsafe IFilterMetadata CreateInstance(IServiceProvider serviceProvider)
        {
            //IL_0000: Unknown result type (might be due to invalid IL)
            //IL_0008: Unknown result type (might be due to invalid IL)
            //IL_000e: Unknown result type (might be due to invalid IL)
            //IL_0025: Unknown result type (might be due to invalid IL)
            //IL_0032: Expected Ref, but got Unknown
            //IL_0046: Unknown result type (might be due to invalid IL)
            if (serviceProvider == (IServiceProvider)0)
            {
                throw new ArgumentNullException("serviceProvider");
            }
            IOptions<MvcOptions> requiredService = serviceProvider.GetRequiredService<IOptions<MvcOptions>>();
            CacheProfile cacheProfile = null;
            if (this.CacheProfileName != null)
            {
                ((IDictionary)(?)requiredService.Value.CacheProfiles).TryGetValue((!0)this.CacheProfileName, ref *(!1*)(&cacheProfile));
                if (cacheProfile == null)
                {
                    throw new InvalidOperationException(Resources.FormatCacheProfileNotFound(this.CacheProfileName));
                }
            }
            this._duration = (this._duration ?? ((cacheProfile != null) ? cacheProfile.Duration : null));
            this._noStore = (this._noStore ?? ((cacheProfile != null) ? cacheProfile.NoStore : null));
            this._location = (this._location ?? ((cacheProfile != null) ? cacheProfile.Location : null));
            this.VaryByHeader = (this.VaryByHeader ?? ((cacheProfile != null) ? cacheProfile.VaryByHeader : null));
            this.VaryByQueryKeys = (this.VaryByQueryKeys ?? ((cacheProfile != null) ? cacheProfile.VaryByQueryKeys : null));
            return new ResponseCacheFilter(new CacheProfile
            {
                Duration = this._duration,
                Location = this._location,
                NoStore = this._noStore,
                VaryByHeader = this.VaryByHeader,
                VaryByQueryKeys = this.VaryByQueryKeys
            });
        }

可以得知Action上设置-----优先级高于--CacheProfiles里面的配置

缓存最终通过ResponseCacheFilter过滤器来实现，ResponseCacheFilter 的代码：

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.Core;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.AspNetCore.ResponseCaching;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;

namespace Microsoft.AspNetCore.Mvc.Internal
{
    /// <summary>
    /// An <see cref="T:Microsoft.AspNetCore.Mvc.Filters.IActionFilter" /> which sets the appropriate headers related to response caching.
    /// </summary>
    public class ResponseCacheFilter : IResponseCacheFilter, IActionFilter, IFilterMetadata
    {
        private readonly CacheProfile _cacheProfile;

        private int? _cacheDuration;

        private ResponseCacheLocation? _cacheLocation;

        private bool? _cacheNoStore;

        private string _cacheVaryByHeader;

        private string[] _cacheVaryByQueryKeys;

        /// <summary>
        /// Gets or sets the duration in seconds for which the response is cached.
        /// This is a required parameter.
        /// This sets "max-age" in "Cache-control" header.
        /// </summary>
        public int Duration
        {
            get
            {
                return (this._cacheDuration ?? this._cacheProfile.Duration) ?? 0;
            }
            set
            {
                this._cacheDuration = value;
            }
        }

        /// <summary>
        /// Gets or sets the location where the data from a particular URL must be cached.
        /// </summary>
        public ResponseCacheLocation Location
        {
            get
            {
                return (this._cacheLocation ?? this._cacheProfile.Location) ?? ResponseCacheLocation.Any;
            }
            set
            {
                this._cacheLocation = value;
            }
        }

        /// <summary>
        /// Gets or sets the value which determines whether the data should be stored or not.
        /// When set to <see langword="true" />, it sets "Cache-control" header to "no-store".
        /// Ignores the "Location" parameter for values other than "None".
        /// Ignores the "duration" parameter.
        /// </summary>
        public bool NoStore
        {
            get
            {
                return (this._cacheNoStore ?? this._cacheProfile.NoStore) ?? false;
            }
            set
            {
                this._cacheNoStore = value;
            }
        }

        /// <summary>
        /// Gets or sets the value for the Vary response header.
        /// </summary>
        public string VaryByHeader
        {
            get
            {
                return this._cacheVaryByHeader ?? this._cacheProfile.VaryByHeader;
            }
            set
            {
                this._cacheVaryByHeader = value;
            }
        }

        /// <summary>
        /// Gets or sets the query keys to vary by.
        /// </summary>
        /// <remarks>
        /// <see cref="P:Microsoft.AspNetCore.Mvc.Internal.ResponseCacheFilter.VaryByQueryKeys" /> requires the response cache middleware.
        /// </remarks>
        public string[] VaryByQueryKeys
        {
            get
            {
                return this._cacheVaryByQueryKeys ?? this._cacheProfile.VaryByQueryKeys;
            }
            set
            {
                this._cacheVaryByQueryKeys = value;
            }
        }

        /// <summary>
        /// Creates a new instance of <see cref="T:Microsoft.AspNetCore.Mvc.Internal.ResponseCacheFilter" />
        /// </summary>
        /// <param name="cacheProfile">The profile which contains the settings for
        /// <see cref="T:Microsoft.AspNetCore.Mvc.Internal.ResponseCacheFilter" />.</param>
        public ResponseCacheFilter(CacheProfile cacheProfile)
        {
            this._cacheProfile = cacheProfile;
        }

        /// <inheritdoc />
        public void OnActionExecuting(ActionExecutingContext context)
        {
            //IL_0008: Unknown result type (might be due to invalid IL)
            //IL_0051: Unknown result type (might be due to invalid IL)
            //IL_00d4: Unknown result type (might be due to invalid IL)
            //IL_0185: Unknown result type (might be due to invalid IL)
            if (context == null)
            {
                throw new ArgumentNullException("context");
            }
            if (!this.IsOverridden(context))
            {
                if (!this.NoStore && !this._cacheProfile.Duration.get_HasValue() && !this._cacheDuration.get_HasValue())
                {
                    throw new InvalidOperationException(Resources.FormatResponseCache_SpecifyDuration("NoStore", "Duration"));
                }
                IHeaderDictionary headers = context.HttpContext.Response.Headers;
                ((IDictionary)(?)headers).Remove((!0)"Vary");
                ((IDictionary)(?)headers).Remove((!0)"Cache-Control");
                ((IDictionary)(?)headers).Remove((!0)"Pragma");
                if (!string.IsNullOrEmpty(this.VaryByHeader))
                {
                    headers["Vary"] = this.VaryByHeader;
                }
                if (this.VaryByQueryKeys != null)
                {
                    IResponseCachingFeature responseCachingFeature = context.HttpContext.Features.Get<IResponseCachingFeature>();
                    if (responseCachingFeature == null)
                    {
                        throw new InvalidOperationException(Resources.FormatVaryByQueryKeys_Requires_ResponseCachingMiddleware("VaryByQueryKeys"));
                    }
                    responseCachingFeature.VaryByQueryKeys = this.VaryByQueryKeys;
                }
                if (this.NoStore)
                {
                    headers["Cache-Control"] = "no-store";
                    if (this.Location == ResponseCacheLocation.None)
                    {
                        headers.AppendCommaSeparatedValues("Cache-Control", "no-cache");
                        headers["Pragma"] = "no-cache";
                    }
                }
                else
                {
                    string text = null;
                    switch (this.Location)
                    {
                    case ResponseCacheLocation.Any:
                        text = "public";
                        break;
                    case ResponseCacheLocation.Client:
                        text = "private";
                        break;
                    case ResponseCacheLocation.None:
                        text = "no-cache";
                        headers["Pragma"] = "no-cache";
                        break;
                    }
                    text = string.Format((IFormatProvider)CultureInfo.get_InvariantCulture(), "{0}{1}max-age={2}", (object)text, (object)((text != null) ? "," : null), (object)this.Duration);
                    if (text != null)
                    {
                        headers["Cache-Control"] = text;
                    }
                }
            }
        }

        /// <inheritdoc />
        public void OnActionExecuted(ActionExecutedContext context)
        {
        }

        internal bool IsOverridden(ActionExecutingContext context)
        {
            //IL_0008: Unknown result type (might be due to invalid IL)
            if (context == null)
            {
                throw new ArgumentNullException("context");
            }
            return Enumerable.Last<IResponseCacheFilter>(Enumerable.OfType<IResponseCacheFilter>((IEnumerable)context.Filters)) != this;
        }
    }
}