异步 HttpContext.Current 为空null 另一种解决方法

using System;
using System.Linq.Expressions;
using System.Reflection;
using System.Threading;
using System.Web;namespace TxSms
{
/// <summary>
/// 解决Asp.net Mvc中使用异步的时候HttpContext.Current为null的方法
/// <remarks>
/// http://www.cnblogs.com/pokemon/p/5116446.html
/// </remarks>
/// </summary>
public static class HttpContextHelper
{
/// <summary>
/// 在同步上下文中查找当前会话<see cref="System.Web.HttpContext" />对象
/// </summary>
/// <param name="context"></param>
/// <returns></returns>
public static HttpContext FindHttpContext(this SynchronizationContext context)
{
if (context == null)
{
return null;
}
var factory = GetFindApplicationDelegate(context);
return factory?.Invoke(context).Context;
} private static Func<SynchronizationContext, HttpApplication> GetFindApplicationDelegate(SynchronizationContext context)
{
Delegate factory = null;
Type type = context.GetType();
if (!type.FullName.Equals("System.Web.LegacyAspNetSynchronizationContext"))
{
return null;
}
//找到字段
ParameterExpression sourceExpression = Expression.Parameter(typeof(SynchronizationContext), "context");
//目前支持 System.Web.LegacyAspNetSynchronizationContext 内部类
//查找 private HttpApplication _application 字段
Expression sourceInstance = Expression.Convert(sourceExpression, type);
FieldInfo applicationFieldInfo = type.GetField("_application", BindingFlags.NonPublic | BindingFlags.Instance);
Expression fieldExpression = Expression.Field(sourceInstance, applicationFieldInfo);
factory = Expression.Lambda<Func<SynchronizationContext, HttpApplication>>(fieldExpression, sourceExpression).Compile(); //返回委托
return ((Func<SynchronizationContext, HttpApplication>)factory);
} /// <summary>
/// 确定异步状态的上下文可用
/// </summary>
/// <param name="context"></param>
/// <returns></returns>
public static HttpContext Check(this HttpContext context)
{
return context ?? (context = SynchronizationContext.Current.FindHttpContext());
}
}
}

using System;
using System.Collections;
using System.Web;
using System.Web.Caching;namespace TxSms
{
/// <summary>
/// HttpRuntime Cache读取设置缓存信息封装
/// <auther>
/// <name>Kencery</name>
/// <date>2015-8-11</date>
/// </auther>
/// 使用描述：给缓存赋值使用HttpRuntimeCache.Set(key,value....)等参数(第三个参数可以传递文件的路径(HttpContext.Current.Server.MapPath()))
/// 读取缓存中的值使用JObject jObject=HttpRuntimeCache.Get(key) as JObject，读取到值之后就可以进行一系列判断
/// </summary>
public static class HttpRuntimeCache
{
/// <summary>
/// 设置缓存时间，配置(从配置文件中读取)
/// </summary>
private const double Seconds = 30 * 24 * 60 * 60; /// <summary>
/// 缓存指定对象，设置缓存
/// </summary>
public static bool Set(string key, object value)
{
return Set(key, value, null, DateTime.Now.AddSeconds(Seconds), Cache.NoSlidingExpiration, CacheItemPriority.Default, null);
} /// <summary>
/// 缓存指定对象，设置缓存
/// </summary>
public static bool Set(string key, object value, string path)
{
try
{
var cacheDependency = new CacheDependency(path);
return Set(key, value, cacheDependency);
}
catch
{
return false;
}
} /// <summary>
/// 缓存指定对象，设置缓存
/// </summary>
public static bool Set(string key, object value, CacheDependency cacheDependency)
{
return Set(key, value, cacheDependency, Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration, CacheItemPriority.Default, null);
} /// <summary>
/// 缓存指定对象，设置缓存
/// </summary>
public static bool Set(string key, object value, double seconds, bool isAbsulute)
{
return Set(key, value, null, (isAbsulute ? DateTime.Now.AddSeconds(seconds) : Cache.NoAbsoluteExpiration),
(isAbsulute ? Cache.NoSlidingExpiration : TimeSpan.FromSeconds(seconds)), CacheItemPriority.Default, null);
} /// <summary>
/// 获取缓存对象
/// </summary>
public static object Get(string key)
{
return GetPrivate(key);
} /// <summary>
/// 判断缓存中是否含有缓存该键
/// </summary>
public static bool Exists(string key)
{
return (GetPrivate(key) != null);
} /// <summary>
/// 移除缓存对象
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
public static bool Remove(string key)
{
if (string.IsNullOrEmpty(key))
{
return false;
}
HttpRuntime.Cache.Remove(key);
return true;
} /// <summary>
/// 移除所有缓存
/// </summary>
/// <returns></returns>
public static bool RemoveAll()
{
IDictionaryEnumerator iDictionaryEnumerator = HttpRuntime.Cache.GetEnumerator();
while (iDictionaryEnumerator.MoveNext())
{
HttpRuntime.Cache.Remove(Convert.ToString(iDictionaryEnumerator.Key));
}
return true;
} /// <summary>
/// 设置缓存
/// </summary>
public static bool Set(string key, object value, CacheDependency cacheDependency, DateTime dateTime,
TimeSpan timeSpan, CacheItemPriority cacheItemPriority, CacheItemRemovedCallback cacheItemRemovedCallback)
{
if (string.IsNullOrEmpty(key) || value == null)
{
return false;
}
HttpRuntime.Cache.Insert(key, value, cacheDependency, dateTime, timeSpan, cacheItemPriority, cacheItemRemovedCallback);
return true;
} /// <summary>
/// 获取缓存
/// </summary>
private static object GetPrivate(string key)
{
return string.IsNullOrEmpty(key) ? null : HttpRuntime.Cache.Get(key);
}
}
}