ConcurrentDictionary - AddOrUpdate问题

Question

我使用下面的代码试图根据字典对象的键更新它的值。

public static ConcurrentDictionary<string, SingleUserStatisticsViewModel> UsersViewModel = new ConcurrentDictionary<string, SingleUserStatisticsViewModel>();

var userSession = new UserSessionStatistic()
{
    Id = "12345", Browser = "Netscape"
};
var userViewModel = new SingleUserStatisticsViewModel()
{
    UserSessionStatistic = userSession,
    StartTime = DateTime.Now
};

//添加第一次

MyStaticClass.UsersViewModel.AddOrUpdate(userViewModel.UserSessionStatistic.Id, userViewModel, (key, model) => model);

//尝试更新

        var userSession2 = new UserSessionStatistic()
        {
            Id = "12345",
            Browser = "not getting updated????"
        };
        var userViewModel2 = new SingleUserStatisticsViewModel()
        {
            UserSessionStatistic = userSession2,
            StartTime = DateTime.Now
        };

MyStaticClass.UsersViewModel.AddOrUpdate(userViewModel2.UserSessionStatistic.Id, userViewModel2, (key, model) => model);

但是，UsersessionStatistic对象在userViewModel2中并没有在ConcurrentDictionary中得到更新(它的浏览器属性仍然说明了"Netscape")，我做错了什么？

Answer 1

关于价值工厂，医生说

updateValueFactory类型: System.Func :用于根据密钥的现有值为现有密钥生成新值的函数

这意味着你把现有的价值传递给它。您需要用新的更新来更新它：

MyStaticClass.UsersViewModel.AddOrUpdate(userViewModel2.UserSessionStatistic.Id,
                                         userViewModel2, 
                                         (key, oldModel) => userViewModel2);