HttpContextAccessor In ASP.Net Core 2.1
https://github.com/dotnet/aspnetcore/blob/v2.1.33/src/Http/Http/src/HttpContextAccessor.cs
public class HttpContextAccessor : IHttpContextAccessor
{
private static AsyncLocal<HttpContext> _httpContextCurrent = new AsyncLocal<HttpContext>();
public HttpContext HttpContext
{
get
{
return _httpContextCurrent.Value;
}
set
{
_httpContextCurrent.Value = value;
}
}
}
HttpContextAccessor In ASP.Net Core 6.0
https://github.com/dotnet/aspnetcore/blob/v6.0.4/src/Http/Http/src/HttpContextAccessor.cs
/// <summary>
/// Provides an implementation of <see cref="IHttpContextAccessor" /> based on the current execution context.
/// </summary>
public class HttpContextAccessor : IHttpContextAccessor
{
private static readonly AsyncLocal<HttpContextHolder> _httpContextCurrent = new AsyncLocal<HttpContextHolder>();
/// <inheritdoc/>
public HttpContext? HttpContext
{
get
{
return _httpContextCurrent.Value?.Context;
}
set
{
var holder = _httpContextCurrent.Value;
if (holder != null)
{
// Clear current HttpContext trapped in the AsyncLocals, as its done.
holder.Context = null;
}
if (value != null)
{
// Use an object indirection to hold the HttpContext in the AsyncLocal,
// so it can be cleared in all ExecutionContexts when its cleared.
_httpContextCurrent.Value = new HttpContextHolder { Context = value };
}
}
}
private class HttpContextHolder
{
public HttpContext? Context;
}
}
解決AsyncLocal在await環境中會發生複製，導致不能及時清除歷史的HttpContext的問題。