MergeObjectCommand.cs

using System;
using System.Collections.Generic;
using System.Management.Automation;

namespace MyCmdlets
{
    [Cmdlet(VerbsData.Merge, "Object")]
    public class MergeObjectCommand : PSCmdlet
    {
        [Parameter(ValueFromPipeline = true, Mandatory = true)]
        public PSObject[] InputObject;

        private List<PSObject> objects;

        protected override void BeginProcessing()
        {
            objects = new List<PSObject>();
        }

        protected override void ProcessRecord()
        {
            foreach (var obj in InputObject)
                objects.Add(obj);
        }

        protected override void EndProcessing()
        {
            // do work on this.objects here
        }
    }
}