60 lines
2.5 KiB
C#
60 lines
2.5 KiB
C#
using Microsoft.AspNetCore.Http;
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using System;
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using System.Linq.Expressions;
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using System.Reflection;
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using System.Threading;
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namespace Microsoft.AspNetCore.Http
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{
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public static class HttpContextLocal
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{
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private static Func<object> _asyncLocalAccessor;
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private static Func<object, object> _holderAccessor;
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private static Func<object, HttpContext> _httpContextAccessor;
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/// <summary>
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/// 获取当前 HttpContext 对象
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/// </summary>
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/// <returns></returns>
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public static HttpContext Current()
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{
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var asyncLocal = (_asyncLocalAccessor ??= CreateAsyncLocalAccessor())();
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if (asyncLocal == null) return null;
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var holder = (_holderAccessor ??= CreateHolderAccessor(asyncLocal))(asyncLocal);
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if (holder == null) return null;
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return (_httpContextAccessor ??= CreateHttpContextAccessor(holder))(holder);
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// 创建异步本地访问器
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static Func<object> CreateAsyncLocalAccessor()
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{
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var fieldInfo = typeof(HttpContextAccessor).GetField("_httpContextCurrent", BindingFlags.Static | BindingFlags.NonPublic);
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var field = Expression.Field(null, fieldInfo);
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return Expression.Lambda<Func<object>>(field).Compile();
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}
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// 创建常驻 HttpContext 访问器
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static Func<object, object> CreateHolderAccessor(object asyncLocal)
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{
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var holderType = asyncLocal.GetType().GetGenericArguments()[0];
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var method = typeof(AsyncLocal<>).MakeGenericType(holderType).GetProperty("Value").GetGetMethod();
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var target = Expression.Parameter(typeof(object));
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var convert = Expression.Convert(target, asyncLocal.GetType());
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var getValue = Expression.Call(convert, method);
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return Expression.Lambda<Func<object, object>>(getValue, target).Compile();
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}
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// 获取 HttpContext 访问器
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static Func<object, HttpContext> CreateHttpContextAccessor(object holder)
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{
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var target = Expression.Parameter(typeof(object));
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var convert = Expression.Convert(target, holder.GetType());
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var field = Expression.Field(convert, "Context");
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var convertAsResult = Expression.Convert(field, typeof(HttpContext));
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return Expression.Lambda<Func<object, HttpContext>>(convertAsResult, target).Compile();
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}
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}
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}
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}
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