.net core Session会话

ASP.NET Core 应用在默认情况下会利用缓存来存储会话状态，并且默认采用的是分布式缓存。由于演示实例采用基于 Redis 数据库的分布式缓存，所以需要添加针对NuGet包“Microsoft.Extensions.Caching.Redis”的依赖。如下面的代码片段所示，我们调用 IServiceCollection 接口的 AddDistributedRedisCache 扩展方法添加了基于DistributedRedisCache 的服务注册。SessionMiddleware 中间件的注册则通过调用该 IApplication Builder接口的UseSession扩展方法来完成。

using ConsoleApp7;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Caching.Redis;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.FileSystemGlobbing;
using System.Diagnostics;
using System.Text;

Host.CreateDefaultBuilder().ConfigureWebHostDefaults(webHost =>
{
    webHost.ConfigureServices(services =>
    {
        services.AddDistributedRedisCache(redis =>
        {
            redis.InstanceName = "session";
            redis.Configuration = "192.168.0.190";

        });
        services.AddSession();
    });
    webHost.Configure(config =>
    {
        config.UseSession();
        config.Run((httpContext) =>
        {
            string test = httpContext.Session.GetString("test");
            httpContext.Response.ContentType = "text/plain;charset=utf-8";
　　　　　　　　　httpContext.Session.LoadAsync();//首先异步加载会话状态以便后面操作Session
            if (string.IsNullOrEmpty(test))
            {
                test = "test" + DateTime.Now.ToString();
                httpContext.Session.SetString("test", test);
                httpContext.Response.WriteAsync("没有取到session");
            }
            else
            {
                httpContext.Response.WriteAsync(test);
            }
            return Task.CompletedTask;
        });
    });

}).Build().Run();

测试结果

 

如果有这个保存当前会话状态的Session Key，当会话状态在采用默认的分布式缓存进行存储时，整个数据字典（包括Key和Value）会采用预定义的格式序列化成字节数组，基于会话状态的缓存默认采用的是基于滑动时间的过期策略，默认采用的滑动过期时间为20分（12 000 000 000纳秒）。

Session操作源码

 

File: SessionExtensions.cs
Web Access
Project: src\src\Http\Http.Extensions\src\Microsoft.AspNetCore.Http.Extensions.csproj (Microsoft.AspNetCore.Http.Extensions)
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Text;
 
namespace Microsoft.AspNetCore.Http;
 
/// <summary>
/// Extension methods for <see cref="ISession"/>.
/// </summary>
public static class SessionExtensions
{
    /// <summary>
    /// Sets an int value in the <see cref="ISession"/>.
    /// </summary>
    /// <param name="session">The <see cref="ISession"/>.</param>
    /// <param name="key">The key to assign.</param>
    /// <param name="value">The value to assign.</param>
    public static void SetInt32(this ISession session, string key, int value)
    {
        var bytes = new byte[]
        {
                (byte)(value >> 24),
                (byte)(0xFF & (value >> 16)),
                (byte)(0xFF & (value >> 8)),
                (byte)(0xFF & value)
        };
        session.Set(key, bytes);
    }
 
    /// <summary>
    /// Gets an int value from <see cref="ISession"/>.
    /// </summary>
    /// <param name="session">The <see cref="ISession"/>.</param>
    /// <param name="key">The key to read.</param>
    public static int? GetInt32(this ISession session, string key)
    {
        var data = session.Get(key);
        if (data == null || data.Length < 4)
        {
            return null;
        }
        return data[0] << 24 | data[1] << 16 | data[2] << 8 | data[3];
    }
 
    /// <summary>
    /// Sets a <see cref="string"/> value in the <see cref="ISession"/>.
    /// </summary>
    /// <param name="session">The <see cref="ISession"/>.</param>
    /// <param name="key">The key to assign.</param>
    /// <param name="value">The value to assign.</param>
    public static void SetString(this ISession session, string key, string value)
    {
        session.Set(key, Encoding.UTF8.GetBytes(value));
    }
 
    /// <summary>
    /// Gets a string value from <see cref="ISession"/>.
    /// </summary>
    /// <param name="session">The <see cref="ISession"/>.</param>
    /// <param name="key">The key to read.</param>
    public static string? GetString(this ISession session, string key)
    {
        var data = session.Get(key);
        if (data == null)
        {
            return null;
        }
        return Encoding.UTF8.GetString(data);
    }
 
    /// <summary>
    /// Gets a byte-array value from <see cref="ISession"/>.
    /// </summary>
    /// <param name="session">The <see cref="ISession"/>.</param>
    /// <param name="key">The key to read.</param>
    public static byte[]? Get(this ISession session, string key)
    {
        session.TryGetValue(key, out var value);
        return value;
    }
}
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 SessionOptions 源码

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Session;
 
namespace Microsoft.AspNetCore.Builder;
 
/// <summary>
/// Represents the session state options for the application.
/// </summary>
public class SessionOptions
{
    private CookieBuilder _cookieBuilder = new SessionCookieBuilder();
 
    /// <summary>
    /// Determines the settings used to create the cookie.
    /// </summary>
    /// <remarks>
    /// <list type="bullet">
    /// <item><description><see cref="CookieBuilder.Name"/> defaults to <see cref="SessionDefaults.CookieName"/>.</description></item>
    /// <item><description><see cref="CookieBuilder.Path"/> defaults to <see cref="SessionDefaults.CookiePath"/>.</description></item>
    /// <item><description><see cref="CookieBuilder.SameSite"/> defaults to <see cref="SameSiteMode.Lax"/>.</description></item>
    /// <item><description><see cref="CookieBuilder.HttpOnly"/> defaults to <c>true</c>.</description></item>
    /// <item><description><see cref="CookieBuilder.IsEssential"/> defaults to <c>false</c>.</description></item>
    /// </list>
    /// </remarks>
    public CookieBuilder Cookie
    {
        get => _cookieBuilder;
        set => _cookieBuilder = value ?? throw new ArgumentNullException(nameof(value));
    }
 
    /// <summary>
    /// The IdleTimeout indicates how long the session can be idle before its contents are abandoned. Each session access
    /// resets the timeout. Note this only applies to the content of the session, not the cookie.
    /// </summary>
    public TimeSpan IdleTimeout { get; set; } = TimeSpan.FromMinutes(20);
 
    /// <summary>
    /// The maximum amount of time allowed to load a session from the store or to commit it back to the store.
    /// Note this may only apply to asynchronous operations. This timeout can be disabled using <see cref="Timeout.InfiniteTimeSpan"/>.
    /// </summary>
    public TimeSpan IOTimeout { get; set; } = TimeSpan.FromMinutes(1);
 
    private sealed class SessionCookieBuilder : CookieBuilder
    {
        public SessionCookieBuilder()
        {
            Name = SessionDefaults.CookieName;
            Path = SessionDefaults.CookiePath;
            SecurePolicy = CookieSecurePolicy.None;
            SameSite = SameSiteMode.Lax;
            HttpOnly = true;
            // Session is considered non-essential as it's designed for ephemeral data.
            IsEssential = false;
        }
 
        public override TimeSpan? Expiration
        {
            get => null;
            set => throw new InvalidOperationException(nameof(Expiration) + " cannot be set for the cookie defined by " + nameof(SessionOptions));
        }
    }
}