Powershell Command in C#

Along the lines of Keith's approach

using System;
using System.Management.Automation;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var script = @" 
                Get-WmiObject -list -namespace root\cimv2 | Foreach {$_.Name}
            ";

            var powerShell = PowerShell.Create();
            powerShell.AddScript(script);

            foreach (var className in powerShell.Invoke())
            {
                Console.WriteLine(className);
            }
        }
    }
}

I'm not sure why you mentioned PowerShell; you can do this in pure C# and WMI (the System.Management namespace, that is).

To get a list of all WMI classes, use the SELECT * FROM Meta_Class query:

using System.Management;
...

try
{
    EnumerationOptions options = new EnumerationOptions();
    options.ReturnImmediately = true;
    options.Rewindable = false;

    ManagementObjectSearcher searcher =
        new ManagementObjectSearcher("root\\cimv2", "SELECT * FROM Meta_Class", options);

    ManagementObjectCollection classes = searcher.Get();

    foreach (ManagementClass cls in classes)
    {
        Console.WriteLine(cls.ClassPath.ClassName);
    }
}
catch (ManagementException exception)
{
    Console.WriteLine(exception.Message);
}

Just to note that there is a tool available that allows you to create, run, and save WMI scripts written in PowerShell, the PowerShell Scriptomatic tool, available for download from the Microsoft TechNet site.

Using this tool, you could explore all of the WMI classes within the root\CIMV2 or any other WMI namespace.