To perform an asynchronous query on a System Center 2012 Configuration Manager client Windows Instrumentation (WMI) namespace, create a ManagementObjectSearcher object that specifies a WQL query. You then create a ManagementOperationObserver that specifies an event handler for each query result and also for the end of the query.
The asynchronous query is run when the ManagementObjectSearcher object Get method is called with the ManagementOperationObserver object.
To perform an asynchronous query
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Set up a connection to the System Center 2012 Configuration Manager client WMI namespace. For more information, see How to Connect to the Configuration Manager Client WMI Namespace by Using System.Management.
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Create a ManagementObjectSearcher object.
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Create a ManagementOperationObserver object.
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Add an ObjectReadyEventHandler method the ManagementOperationObserver object.
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Add a CompletedEventHandler method to the ManagementOperationObserver.
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Call the ManagementObjectSearcher object Get method and supply the ManagmentOperationObserver object as a parameter.
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Ensure you application still runs while the query is run.
Example
The following C# code example asynchronously queries for components that are installed on a client.
For information about calling the sample code, see How to Call a WMI Class Method by Using System.Management.
C# | Copy Code |
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public void EnumerateInstancesAsync(ManagementScope scope) { try { // Instantiate an object searcher with the query. ManagementObjectSearcher searcher = new ManagementObjectSearcher(scope, new SelectQuery("CCM_InstalledComponent")); // Create a results watcher object // and handler for results and completion. ManagementOperationObserver results = new ManagementOperationObserver(); // Attach handler to events for results and completion. results.ObjectReady += new ObjectReadyEventHandler(this.NewObject); results.Completed += new CompletedEventHandler(this.Done); Console.WriteLine("Installed Components"); Console.WriteLine("--------------------"); Console.WriteLine(); // Call the asynchronous overload of Get() // to start the enumeration. searcher.Get(results); // Do something else while results // arrive asynchronously. while (!this.Completed) { System.Threading.Thread.Sleep(1000); } this.Reset(); } catch (ManagementException e) { Console.WriteLine("Failed to run query: " + e.Message); throw; } } private bool isCompleted = false; private void NewObject(object sender, ObjectReadyEventArgs obj) { try { Console.WriteLine("Name: {0}, Version = {1}", obj.NewObject["DisplayName"], obj.NewObject["Version"]); } catch (ManagementException e) { Console.WriteLine("Error: " + e.Message); } } private bool Completed { get { return isCompleted; } } private void Reset() { isCompleted = false; } private void Done(object sender, CompletedEventArgs obj) { isCompleted = true; } |
This example method has the following parameters:
Parameter | Type | Description |
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Scope |
ManagementScope |
A valid ManagementScope. The path should be root\ccm. |
Compiling the Code
Namespaces
System.
System.Management.
Assembly
System.Management.
Robust Programming
The exception that can be raised is System.Management.ManagementException.
See Also
Tasks
How to Call a WMI Class Method by Using System.ManagementHow to Connect to the Configuration Manager Client WMI Namespace by Using System.Management
How to Perform a Synchronous Query by Using System.Management
How to Read a WMI Object by Using System.Management