可以使用基于 Cookie 的会话共享。

1. 在 Asp.Net Webforms 的项目中，设置 Cookie 名称和过期时间：

protected void Application_Start(object sender, EventArgs e)
{
    // 设置 Cookie 名称
    SessionStateConfig.CookieName = ".AspNetCore.Session";

    // 设置过期时间
    SessionStateConfig.CookieExpiration = TimeSpan.FromDays(1);
}

2. 在 Asp.Net Core 项目的 Startup.cs 中，启用 Cookie：

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    // 启用 Cookie
    services.Configure(options => {
        options.CheckConsentNeeded = context => true;
        options.MinimumSameSitePolicy = SameSiteMode.None;
    });
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Error");
        app.UseHsts();
    }

    app.UseHttpsRedirection();
    app.UseStaticFiles();

    // 启用 Cookie
    app.UseCookiePolicy();

    app.UseSession();

    app.UseMvc();
}

3. 在 Asp.Net Core 项目的 Controller 中，获取 Webforms 项目中设置的 Cookie 并将其值赋给当前会话：

public HomeController(IHttpContextAccessor httpContextAccessor)
{
    _httpContextAccessor = httpContextAccessor;
}

public IActionResult Index()
{
    var cookieValue = _httpContextAccessor.HttpContext.Request.Cookies[".AspNetCore.Session"];

    if (!string.IsNullOrEmpty(cookieValue))
    {
        HttpContext.Session.LoadFromBase64(cookieValue);
    }

    return View();
}

4. 在 Asp.Net Webforms 项目中，获取 Asp.Net Core 项目中设置的 Session 并将其值赋给当前会话：

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        var sessionId = Request.Cookies[".AspNetCore.Session"].Value;

        using (var httpClient = new HttpClient())
        {
            var response = httpClient.GetAsync($"https://{Constants.CoreSiteUrl}/api/session/{sessionId}").Result;
            var session