尝试访问USB设备时，RPC_E_CANTCALLOUT_ININPUTSYNCCALL [英] RPC_E_CANTCALLOUT_ININPUTSYNCCALL when trying to access USB device

问题描述

我有这段代码：

var searcher = new ManagementObjectSearcher("root\\CIMV2", "SELECT * FROM Win32_DiskDrive");              
foreach (var queryObj in searcher.Get().Cast<ManagementObject>()) //Error points to this line

这个代码基本上是这样的，它运行在连接的设备列表中，看看我想要的是否连接。
如果在代码运行时设备已经连接的时候运行这个代码，那么这个代码是完美无缺的。
但是如果我用DBT_DEVICEARRIVAL（这是系统发送的事件，当某个设备连接，我抓住它与

Basically what this code does is, it runs through a list of connected devices and looks if the one i want is connected. If I run this code while the device is already connected at the time when the code is ran, then it works flawlessly. But if I trigger this code with DBT_DEVICEARRIVAL (which is event the system sends when some device is connected and i catch it with

private static IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled){if(..DBT_DEVICEARRIVAL..) new ScanDevices(); /*Here lies the code from above (in the class)*/}

）我得到这个错误：

由于应用程序正在调度输入同步调用，所以无法进行呼出。 （HRESULT的异常：0x8001010D（RPC_E_CANTCALLOUT_ININPUTSYNCCALL））。

An outgoing call cannot be made since the application is dispatching an input-synchronous call. (Exception from HRESULT: 0x8001010D (RPC_E_CANTCALLOUT_ININPUTSYNCCALL)).

如果我将thread.sleep（5000）放在上面的代码之上，那么在执行之前等待5秒钟，那么代码工作。所以冲突必须在某个地方，其他的东西首先尝试访问该设备，并将其全部用于自己。

If I put thread.sleep(5000) on top of the code above, so it waits 5 seconds before executing, then the code works. So the conflict must be somewhere, where other things try to access that device first and hog it all for themselves.

我搜索互联网，发现建议，如发送自定义postmessage我自己来触发代码，但我对如何做到这一点没有什么意见，甚至如何解决这个问题。

I searched the internet and found suggestions like sending custom postmessage to myself to trigger the code, but I have little idea on how to do that, or even how would that solved the problem.

这里最好的解决方案是什么？ p>

What is the best solution here?

推荐答案

将代码换成新线程：

Thread thread = new Thread(() =>
{
    ManagementObjectSearcher theSearcher = new ManagementObjectSearcher("SELECT * FROM Win32_DiskDrive");
    foreach (ManagementObject currentObject in theSearcher.Get())
    {
        Debug.WriteLine("Device present: " + currentObject);          
        ManagementObject theSerialNumberObjectQuery = new ManagementObject("Win32_PhysicalMedia.Tag='" + currentObject["DeviceID"] + "'");
        serial = theSerialNumberObjectQuery["SerialNumber"].ToString();
    }
});
thread.Start();
thread.Join(); //wait for the thread to finish

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