c# - 代码没有遍历整个字典？

Question

我遇到了一个问题，但我不知道自己做错了什么。我尝试了无数不同的东西，但出于某种原因，它就是行不通。我的主循环:

static Dictionary<string, int> dict = new Dictionary<string, int>();

public static void IterateOverEachUser()
{
    if (dict.Count > 0) {
        foreach (KeyValuePair<string, int> item in dict.ToList())
        {
            string userName = item.Key;
            int amountLeft = item.Value;
            if(amountLeft == 60)
            {
                Log(userName + " started!");
            }
            Log(userName + amountLeft);
            dict[userName] = dict[userName] - 1;
            amountLeft = item.Value;
            if(amountLeft == 0)
            {
                Log(userName + " ran out!");
            }
        }
    }
}

public static void AddUser(string User)
{
    if (dict.ContainsKey(User))
    {
        Log("User already exists.");
    }
    else
    {
        dict.Add(User,60);
        Log("User has been added.");
    }
}

我每 5 秒循环一次 IterateOverEachUser()。当我使用该方法添加一个用户时，一切都很好，但是当我添加第二个时，他的值停留在 60 而另一个不断滚动。

有人知道为什么会这样吗？我来自使用 HashMaps 的 Java，并使用相同的代码按预期工作。 (即:迭代每个用户，所有用户的值都减去 1，然后停止，直到 5 秒循环再次调用 IterateOverEachUser() 方法)。

提前致谢!

Answer 1

amountLeft = item.Value; 会产生错误的值(旧值)。

此外，在使用计时器和静态资源时，最好使用 lock 使您的方法线程安全。

下面的测试代码非常适合我:

static Dictionary<string, int> dict = new Dictionary<string, int>();
static object lockObject = new Object();

public static void IterateOverEachUser()
{
    lock (lockObject)
    {
        if (dict.Count > 0)
        {
            foreach (KeyValuePair<string, int> item in dict.ToList())
            {
                string userName = item.Key;
                int amountLeft = item.Value;
                if (amountLeft == 60)
                {
                    Console.WriteLine(userName + " started!");
                }
                Console.WriteLine(userName + amountLeft);
                dict[userName] = dict[userName] - 1;
                amountLeft = dict[userName];
                if (amountLeft == 0)
                {
                    Console.WriteLine(userName + " ran out!");
                }

                Console.WriteLine("User " + item.Key + " = " + amountLeft);
            }
        }
    }
}

public static void AddUser(string User)
{
    if (dict.ContainsKey(User))
    {
        Console.WriteLine("User already exists.");
    }
    else
    {
        dict.Add(User, 60);
        Console.WriteLine("User has been added.");
    }
}

static void Main(string[] args)
{

    AddUser("U1");
    AddUser("U2");

    int counter = 1;
    System.Timers.Timer t1 = new System.Timers.Timer();
    t1.Interval = 5000;
    t1.Elapsed += (oo, ee) => 
    {
        IterateOverEachUser();

        if (counter++ == 5)
            AddUser("U3");
    };

    t1.Start();

    Console.ReadKey();
}

输出:

User has been added.
User has been added.
U1 started!
U160
User U1 = 59
U2 started!
U260
User U2 = 59
U159
User U1 = 58
U259
User U2 = 58
U158
User U1 = 57
U258
User U2 = 57
U157
User U1 = 56
U257
User U2 = 56
U156
User U1 = 55
U256
User U2 = 55
User has been added.
U155
User U1 = 54
U255
User U2 = 54
U3 started!
U360
User U3 = 59
U154
User U1 = 53
U254
User U2 = 53
U359
User U3 = 58
U153
User U1 = 52
U253
User U2 = 52
U358
User U3 = 57
// and so one