using System.Management.Automation;

namespace HelloPowerShell
{
    [Cmdlet(VerbsCommon.Get, "HelloCmdlet")]
    public class HelloCmdlet : Cmdlet
    {
        protected override void ProcessRecord()
        {
            WriteObject("Hello World!");
        }
    }
}

<?xml version="1.0" encoding="utf-8" ?>
<helpItems xmlns="http://msh" schema="maml">
  <command:command xmlns:maml="http://schemas.microsoft.com/maml/2004/10" 
           xmlns:command="http://schemas.microsoft.com/maml/dev/command/2004/10" 
           xmlns:dev="http://schemas.microsoft.com/maml/dev/2004/10">
    <command:details>
      <command:name>
        hellocmdlet
      </command:name>
      <maml:description>
        <maml:para>hellocmdlet</maml:para>
      </maml:description>
      <maml:copyright>
        <maml:para>Copyright</maml:para>
      </maml:copyright>
      <command:verb></command:verb>
      <command:noun></command:noun>
    </command:details>
    <maml:description>
      <maml:para>
        hellocmdlet description
      </maml:para>
    </maml:description>
  </command:command>
</helpItems>

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Management.Automation;
using System.Management.Automation.Runspaces;

namespace HelloPowerShell
{
    [RunInstaller(true)]
    public class HelloSnapIn : CustomPSSnapIn
    {
        private Collection<CmdletConfigurationEntry> _cmdlets;

        /// <summary>
        /// Gets description of powershell snap-in.
        /// </summary>
        public override string Description
        {
            get { return "A Description of HelloCmdlet"; }
        }

        /// <summary>
        /// Gets name of power shell snap-in
        /// </summary>
        public override string Name
        {
            get { return "HelloCmdlet"; }
        }

        /// <summary>
        /// Gets name of the vendor
        /// </summary>
        public override string Vendor
        {
            get { return ""; }
        }

        public override Collection<CmdletConfigurationEntry> Cmdlets
        {
            get
            {
                if (null == _cmdlets)
                {
                    _cmdlets = new Collection<CmdletConfigurationEntry>();
                    _cmdlets.Add(new CmdletConfigurationEntry
                      ("Get-HelloCmdlet", typeof(HelloCmdlet), "Get-HelloCmdlet.dll-Help.xml"));
                }
                return _cmdlets;
            }
        }

    }
}