hr = CoCreateInstance(
           CLSID_MMDeviceEnumerator, NULL,
           CLSCTX_ALL, IID_IMMDeviceEnumerator,
           (void**)&pEnumerator);

这个地方可能找不到链接库，
error LNK2019: unresolved external symbol _CLSID_MMDeviceEnumerator
error LNK2019: unresolved external symbol _IID_IMMDeviceEnumerator

解决方法
hr = CoCreateInstance(
           __uuidof(MMDeviceEnumerator), NULL,
           CLSCTX_ALL, __uuidof(IMMDeviceEnumerator),
           (void**)&pEnumerator);

缺少 PKEY_Device_FriendlyName
hr = pProps->GetValue(PKEY_Device_FriendlyName, &varName);

解决方法是 #include <functiondiscoverykeys.h>  // PKEY_Device_FriendlyName