情况就是这样。
我在做什么： - ASP.NET MVC 4 Web API - IIS 7.0来托管应用程序 - C＃
我有Web API从Intranet上的远程计算机获取性能数据，并且正在测试通过URL调用调用API，这将返回JSON。但是，它必须在返回JSON之前先完成执行。因此，例如，如果我将性能监控返回10秒，我将需要等待10秒才能显示所有数据值。
我想要做的就是让它生效，这样当它每秒读取性能计数器并以JSON显示它时会返回一个值，而不是等待检索所有内容然后立即列出所有内容。我试图使用YIELD关键字来完成此任务，但它仍然无法正常工作。在方法完成之前，JSON不会显示在浏览器中。
以下是存储库方法和协调控制器操作的代码：
来自LogDBRepository.cs：
public IEnumerable<DataValueInfo> LogTimedPerfDataLive(string macName, string categoryName, string counterName,
string instanceName, string logName, long? seconds)
{
iModsDBRepository modsDB = new iModsDBRepository();
List<MachineInfo> theMac = modsDB.GetMachineByName(macName);
if (theMac.Count == 0)
yield break;
else if (instanceName == null)
{
if (!PerformanceCounterCategory.Exists(categoryName, macName) ||
!PerformanceCounterCategory.CounterExists(counterName, categoryName, macName))
{
yield break;
}
}
else if (instanceName != null)
{
if (!PerformanceCounterCategory.Exists(categoryName, macName) ||
!PerformanceCounterCategory.CounterExists(counterName, categoryName, macName) ||
!PerformanceCounterCategory.InstanceExists(instanceName, categoryName, macName))
{
yield break;
}
}
else if (logName == null)
{
yield break;
}
// Check if entered log name is a duplicate for the authenticated user
List<LogInfo> checkDuplicateLog = this.GetSingleLog(logName);
if (checkDuplicateLog.Count > 0)
{
yield break;
}
PerformanceCounterCategory category = new PerformanceCounterCategory(categoryName, theMac[0].MachineName);
if (category.CategoryName == null || category.MachineName == null)
{
yield break;
}
List<LogInfo> logIt = new List<LogInfo>();
if (category.CategoryType != PerformanceCounterCategoryType.SingleInstance)
{
List<InstanceInfo> instances = modsDB.GetInstancesFromCatMacName(theMac[0].MachineName, category.CategoryName);
foreach (InstanceInfo inst in instances)
{
if (!category.InstanceExists(inst.InstanceName))
{
continue;
}
else if (inst.InstanceName.Equals(instanceName, StringComparison.OrdinalIgnoreCase))
{
PerformanceCounter perfCounter = new PerformanceCounter(categoryName, counterName,
inst.InstanceName, theMac[0].MachineName);
//CounterSample data = perfCounter.NextSample();
//double value = CounterSample.Calculate(data, perfCounter.NextSample());
string data = "";
List<UserInfo> currUser = this.GetUserByName(WindowsIdentity.GetCurrent().Name);
string timeStarted = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
List<string> dataValues = new List<string>();
for (int i = 0; i < seconds; i++)
{
data = "Value " + i + ": " + perfCounter.NextValue().ToString();
DataValueInfo datItUp = new DataValueInfo
{
Value = data
};
yield return datItUp;
dataValues.Add(data);
Thread.Sleep(1000);
}
string timeFinished = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
Log log = new Log
{
LogName = logName,
CounterName = perfCounter.CounterName,
InstanceName = perfCounter.InstanceName,
CategoryName = perfCounter.CategoryName,
MachineName = perfCounter.MachineName,
TimeStarted = timeStarted,
TimeFinished = timeFinished,
PerformanceData = string.Join(",", dataValues),
UserID = currUser[0].UserID
};
this.CreateLog(log);
break;
}
}
}
else
{
PerformanceCounter perfCounter = new PerformanceCounter(categoryName, counterName,
"", theMac[0].MachineName);
string data = "";
List<UserInfo> currUser = this.GetUserByName(WindowsIdentity.GetCurrent().Name);
string timeStarted = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
List<string> dataValues = new List<string>();
for (int i = 0; i < seconds; i++)
{
data = "Value " + i + ": " + perfCounter.NextValue().ToString();
DataValueInfo datItUp = new DataValueInfo
{
Value = data
};
yield return datItUp;
dataValues.Add(data);
Thread.Sleep(1000);
}
string timeFinished = DateTime.Now.ToString("MM/dd/yyyy - h:mm:ss tt");
Log log = new Log
{
LogName = logName,
CounterName = perfCounter.CounterName,
InstanceName = perfCounter.InstanceName,
CategoryName = perfCounter.CategoryName,
MachineName = perfCounter.MachineName,
TimeStarted = timeStarted,
TimeFinished = timeFinished,
PerformanceData = string.Join(",", dataValues),
UserID = currUser[0].UserID
};
this.CreateLog(log);
}
}
来自LogController.cs：
[AcceptVerbs("GET", "POST")]
public IEnumerable<DataValueInfo> Log_Perf_Data(string machine_name, string category_name, string counter_name, string instance_name,
string log_name, long? seconds, string live, string enforceQuery)
{
LogController.CheckUser();
// POST api/log/post_data?machine_name=&category_name=&counter_name=&instance_name=&log_name=&seconds=
if (machine_name != null && category_name != null && counter_name != null && log_name != null && seconds.HasValue && enforceQuery == null)
{
List<DataValueInfo> dataVal = logDB.LogTimedPerfDataLive(machine_name, category_name, counter_name, instance_name,
log_name, seconds).ToList();
logDB.SaveChanges();
foreach (var val in dataVal)
yield return val;
}
yield break;
}
感谢您的时间和考虑。
答案 0 :(得分：1)
yield仅在刷新响应时创建要返回的内存对象。
执行此操作的最简单方法可能是将json保存在服务器上的同步（静态？）变量中，当您请求显示您创建json的性能数据时，启动后台工作者（google for web backgrounder nuget）填充将数据转换为json对象，设置运行标志并返回json对象（开始时可能为空）。
然后，使用浏览器中的setInterval，每秒通过调用服务器来刷新此数据，因此每次获得包含越来越多数据的响应时。当后台线程完成时，你将running flag设置为false，并在下一次调用中返回你的json信息，这样你就可以停止从客户端刷新。
这是 NOT 最好的方法，但可能最容易实现。