The bare minimum needed to write a MSMQ sample application

//From Windows Service, use this code
MessageQueue messageQueue = null;
if (MessageQueue.Exists(@".\Private$\SomeTestName"))
{
    messageQueue = new MessageQueue(@".\Private$\SomeTestName");
    messageQueue.Label = "Testing Queue";
}
else
{
    // Create the Queue
    MessageQueue.Create(@".\Private$\SomeTestName");
    messageQueue = new MessageQueue(@".\Private$\SomeTestName");
    messageQueue.Label = "Newly Created Queue";
}
messageQueue.Send("First ever Message is sent to MSMQ", "Title");

//From Windows application
MessageQueue messageQueue = new MessageQueue(@".\Private$\SomeTestName");
System.Messaging.Message[] messages = messageQueue.GetAllMessages();

foreach (System.Messaging.Message message in messages)
{
    //Do something with the message.
}
// after all processing, delete all the messages
messageQueue.Purge();

For more complex scenario, you could use Message objects to send the message, wrap your own class object inside it, and mark your class as serializable. Also be sure that MSMQ is installed on your system

Perhaps code below will be useful for someone to just get quick intro to MSMQ.

So to start I suggest that you create 3 apps in a solution:

1. MessageTo (Windows Form) Add 1 button.
2. MessageFrom (Windows Form) Add 1 richtextbox.
3. MyMessage (Class Library) Add 1 class.

Just copy past code and try it. Make sure that MSMQ is installed on your MS Windows and projects 1 and 2 have reference to System.Messaging.

1. MessageTo (Windows Form) Add 1 button.

using System;
using System.Messaging;
using System.Windows.Forms;

namespace MessageTo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {

            #region Create My Own Queue 

            MessageQueue messageQueue = null;
            if (MessageQueue.Exists(@".\Private$\TestApp1"))
            {
                messageQueue = new MessageQueue(@".\Private$\TestApp1");
                messageQueue.Label = "MyQueueLabel";
            }
            else
            {
                // Create the Queue
                MessageQueue.Create(@".\Private$\TestApp1");
                messageQueue = new MessageQueue(@".\Private$\TestApp1");
                messageQueue.Label = "MyQueueLabel";
            }

            #endregion

            MyMessage.MyMessage m1 = new MyMessage.MyMessage();
            m1.BornPoint = DateTime.Now;
            m1.LifeInterval = TimeSpan.FromSeconds(5);
            m1.Text = "Command Start: " + DateTime.Now.ToString();

            messageQueue.Send(m1);
        }
    }
}

2. MessageFrom (Windows Form) Add 1 richtextbox.

using System;
using System.ComponentModel;
using System.Linq;
using System.Messaging;
using System.Windows.Forms;

namespace MessageFrom
{
    public partial class Form1 : Form
    {
        Timer t = new Timer();
        BackgroundWorker bw1 = new BackgroundWorker();
        string text = string.Empty;

        public Form1()
        {
            InitializeComponent();

            t.Interval = 1000;
            t.Tick += T_Tick;
            t.Start();

            bw1.DoWork += (sender, args) => args.Result = Operation1();
            bw1.RunWorkerCompleted += (sender, args) =>
            {
                if ((bool)args.Result)
                {
                    richTextBox1.Text += text;
                }
            };
        }

        private object Operation1()
        {
            try
            {
                if (MessageQueue.Exists(@".\Private$\TestApp1"))
                {
                    MessageQueue messageQueue = new MessageQueue(@".\Private$\TestApp1");
                    messageQueue.Formatter = new XmlMessageFormatter(new Type[] { typeof(MyMessage.MyMessage) });


                    System.Messaging.Message[] messages = messageQueue.GetAllMessages();

                    var isOK = messages.Count() > 0 ? true : false;
                    foreach (System.Messaging.Message m in messages)
                    {
                        try
                        {
                            var command = (MyMessage.MyMessage)m.Body;
                            text = command.Text + Environment.NewLine;
                        }
                        catch (MessageQueueException ex)
                        {
                        }
                        catch (Exception ex)
                        {
                        }
                    }                   
                    messageQueue.Purge(); // after all processing, delete all the messages
                    return isOK;
                }
            }
            catch (MessageQueueException ex)
            {
            }
            catch (Exception ex)
            {
            }

            return false;
        }

        private void T_Tick(object sender, EventArgs e)
        {
            t.Enabled = false;

            if (!bw1.IsBusy)
                bw1.RunWorkerAsync();

            t.Enabled = true;
        }
    }
}

3. MyMessage (Class Library) Add 1 class.

using System;

namespace MyMessage
{
    [Serializable]
    public sealed class MyMessage
    {
        public TimeSpan LifeInterval { get; set; }

        public DateTime BornPoint { get; set; }

        public string Text { get; set; }
    }
}

Enjoy :)