WMI.NET Invalid request

Question

I want to get an "Invalid Query" exception when trying to execute the following query:

ManagementObjectSearcher searcher = new ManagementObjectSearcher("SELECT * FROM Win32_DiskQuota WHERE QuotaVolume.DeviceID = 'C:'"); ManagementObjectCollection quotaCollection = searcher.Get(); 

However, this works: "SELECT * FROM Win32_DiskQuota".

According to MSDN:

For most uses of class descriptors in a WHERE clause, WMI places the request as invalid and returns an error. However, use the dot (.) Operator for the properties of a type object in WMI. For example, the following query is valid if Prop is a valid property of MyClass and is an object type:

SELECT * FROM MyClass WHERE Prop.embedprop = 5

Does this mean that it only works if Prop is declared as an OBJECT?

Here is the exception information:

 System.Management.ManagementException was unhandled HResult=-2146233087 Message=Invalid query Source=System.Management StackTrace:  System.Management.ManagementException.ThrowWithExtendedInfo(ManagementStatus errorCode)  System.Management.ManagementObjectCollection.ManagementObjectEnumerator.MoveNext()  UserQuota.Program.getQuota()  c:\users\administrator\documents\visual studio 2015\Projects\UserQuota\UserQuota\Program.cs: 40  UserQuota.Program.Main(String[] args)  c:\users\administrator\documents\visual studio 2015\Projects\UserQuota\UserQuota\Program.cs: 33  System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)  System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)  Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()  System.Threading.ThreadHelper.ThreadStart_Context(Object state)  System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)  System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)  System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)  System.Threading.ThreadHelper.ThreadStart() InnerException: 

Answer 1

Yes. According to the Win32_DiskQuota documentation, the QuotaVolume property is a reference to the Win32_LogicalDisk WMI class. The quote you quoted from MSDN made the query invalid according to WQL specifications.

Instead, you can use something like this:

 ManagementObjectSearcher searcher = new ManagementObjectSearcher("SELECT * FROM Win32_DiskQuota WHERE QuotaVolume = \"Win32_LogicalDisk.DeviceID=\\\"C:\\\"\""); ManagementObjectCollection quotaCollection = searcher.Get(); 

(Pay attention to all shielding ...)