Question

How do I get the return value of the Format method of the Win32_Volume class ?

I use: public void ManagementObject.InvokeMethod(ManagementOperationObserver watcher, string methodName, Object[] args) that in System.Management, and it has void return signature.

Answer 1

To get the result directly you can use the ManagementObject.InvokeMethod Method (String, ManagementBaseObject, InvokeMethodOptions) version of the InvokeMethod Method.

Like so

using System;
using System.Collections.Generic;
using System.Management;
using System.Text;

namespace GetWMI_Info
{
    class Program
    {
// This method is used to format the volume.

        static void Main(string[] args)
        {
            try
            {
                ManagementScope Scope;                
                Scope = new ManagementScope("\\\\.\\root\\CIMV2", null);

                Scope.Connect();
                ObjectGetOptions Options      = new ObjectGetOptions();
                ManagementPath Path           = new ManagementPath("Win32_Volume.DeviceID=\"\\\\\\\\?\\\\Volume{178edf63-2039-11e2-8012-005056c00008}\\\\\"");
                ManagementObject ClassInstance= new ManagementObject(Scope, Path, Options);
                ManagementBaseObject inParams = ClassInstance.GetMethodParameters("Format");


                ManagementBaseObject outParams= ClassInstance.InvokeMethod("Format", inParams ,null);
                Console.WriteLine("{0,-35} {1,-40}","Return Value",outParams["ReturnValue"]);

            }
            catch (Exception e)
            {
                Console.WriteLine(String.Format("Exception {0} Trace {1}",e.Message,e.StackTrace));
            }
            Console.WriteLine("Press Enter to exit");
            Console.Read();
        }
    }
}

Now if you are using a ManagementOperationObserver for asynchronous execution, you can get the result in the ObjectReady event

Like so

using System;
using System.Collections.Generic;
using System.Management;
using System.Text;

namespace GetWMI_Info
{
    public class InvokeAsync
    {
        public InvokeAsync()
        {

            // Create a results watcher object,
            ManagementOperationObserver results = new ManagementOperationObserver();

            // Attach handler to events for results and completion
            results.ObjectReady += new ObjectReadyEventHandler(this.NewObject);
            results.Completed += new CompletedEventHandler(this.Done);

            ManagementScope Scope;
            Scope = new ManagementScope("\\\\.\\root\\CIMV2", null);

            Scope.Connect();
            ObjectGetOptions Options = new ObjectGetOptions();
            ManagementPath Path = new ManagementPath("Win32_Volume.DeviceID=\"\\\\\\\\?\\\\Volume{178edf63-2039-11e2-8012-005056c00008}\\\\\"");
            ManagementObject ClassInstance = new ManagementObject(Scope, Path, Options);
            ManagementBaseObject inParams = ClassInstance.GetMethodParameters("Format");


            ClassInstance.InvokeMethod(results, "Format", inParams, null);

            while (!this.Completed)
            {
                System.Threading.Thread.Sleep(1000);
            }

            this.Reset();

        }

        private bool isCompleted = false;

        private void NewObject(object sender,
            ObjectReadyEventArgs obj)
        {
            Console.WriteLine("ReturnValue : {0}", obj.NewObject["ReturnValue"]);
        }

        private bool Completed
        {
            get
            {
                return isCompleted;
            }
        }

        private void Reset()
        {
            isCompleted = false;
        }

        private void Done(object sender,
            CompletedEventArgs obj)
        {
            isCompleted = true;
        }

        public static void Main()
        {
            InvokeAsync example =
                new InvokeAsync();

            return;
        }

    }
}