分别显示每个用户 ID 的开始和结束时间

Question

我在每个UserId 上运行foreach 循环，但由于某种原因...在我的xml 中，只有一个userId 与所有@987654325 的所有开始时间和结束时间一起显示@。我需要它分别为每个userId 显示start 和end 时间。

所以它看起来像这样：

User2
Start
End
Start
End
Start
End

它需要看起来像这样：

User1
Start
End
Start
End

User2
Start
End

我的代码：

foreach (String userId in request.Users) // request.Users is a Array of UserId's 
{
    List<UserModel> result = // I am making my DataAccess Layer call here.
    UserRecord record = new UserRecord();
    record.UserId = userId;
    record.TimePeriodList = new List<TimePeriod>();
    for (int i = 0; i < result.Count; i += 2)
    {
        TimePeriod timeData = new TimePeriod();
        timeData.StartTime = result[i].TimeDate;
        // if result count is an odd number and this is the last iteration for the UserId
        if (((result.Count & 1) == 1) && (i == result.Count))
            {
                timeData.EndTime = result[i + 1].TimeDate;
            }
            record.TimePeriodList.Add(timeData);
        }
        response.UserRecordList = new List<UserRecord>();
        response.UserRecordList.Add(record);
}

public class GetUserResponse
{
    private List<UserRecord> userRecordList;

    public List<UserRecord> UserRecordList
    {
        get { return userRecordList; }
        set { userRecordList = value; }
    }
}

public class UserRecord
{
    private string userId;
    private List<TimePeriod> timePeriodList;

    public string UserId
    {
        get { return userId; }
        set { userId = value; }
    }

    public List<TimePeriod> TimePeriodList
    {
        get { return timePeriodList; }
        set { timePeriodList = value; }
    }
}

public class TimePeriod
{
    private DateTime startTime;
    private DateTime endTime;

    public DateTime StartTime
    {
        get { return startTime; }
        set { startTime = value; }
    }

    public DateTime EndTime
    {
        get { return endTime; }
        set { endTime = value; }
    }
}

我从DataAccess 层返回的数据如下所示：

UserId    Time        EventType
Test1   xx-xx-xxxx   Start
Test1   xx-xx-xxxx   End
Test2   xx-xx-xxxx   Start

因此，如果存在奇数，则该 User 的结束时间默认为 DateTime.MinValue。

Answer 1

如果您单步调试程序，注意变量的状态，您可以轻松发现错误。你的代码几乎可以工作，因为你得到了结果。您看到的唯一结果是最后一个用户...

让我们看看你的循环：

// you have created a response object here which I had to infer
var response = new GetUserResponse();  // added so my explanation makes sense

foreach (String userId in request.Users) // request.Users is a Array of UserId's 
{
    List<UserModel> result = // I am making my DataAccess Layer call here.
    UserRecord record = new UserRecord();
    // removed stuff that already works
    response.UserRecordList = new List<UserRecord>();
    response.UserRecordList.Add(record);
}

request.Users 有两个项目，Test1 和 Test2。在 foreach 循环上放置一个断点并开始调试。

如果我们进入 foreach 循环这个状态：

response = instance1 of GetUserResponse
response.UserRecordList = null;
userId = test1

如果我们走到response.UserRecordList = new List<UserRecord>();这一行，这就是状态：

response = instance1 of GetUserResponse
response.UserRecordList = null;
userId = test1
record = instance1 of UserRecord with values in its fields

当我们越过下一行时，状态变为

response.UserRecordList = new instance of List<UserRecord>(); // list1

在循环的最后一行之后，我们的状态是

response.UserRecordList.Length = 1

现在我们从数组中获取下一项，所以userId 变成了 test2。 让我们再次运行到最后一行，直到现在 UserRecordList 仍然有 1 个 UserRecord 但是如果我们越过那行，就会创建一个 NEW 实例，我将其称为 list2：

response.UserRecordList = new instance of List<UserRecord>(); // list2

通过这一步，之前的 list1 不再被引用，稍后将被垃圾回收。在最后一行添加了 test2 的 UserRecord，然后我们就完成了。

显然，创建用户记录列表的行不应该在 foreach 循环内。

修复很简单

var response = new GetUserResponse();  // added so my explanation makes sense
response.UserRecordList = new List<UserRecord>(); // init List once

foreach (String userId in request.Users) // request.Users is a Array of UserId's 
{
    List<UserModel> result = // I am making my DataAccess Layer call here.
    UserRecord record = new UserRecord();
    // removed stuff that already works
    // don't init the UserRecordList here, it is done at the start of the loop.
    response.UserRecordList.Add(record);
}