Basic WCF Call + Callback example

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.ServiceModel;

namespace ClientApp
{
    public partial class Form1 : Form
    {
        bool isSubscribed = false;
        Callback callback;
        ServiceReference1.CalculatorClient client;

        public Form1()
        {
            InitializeComponent();
            callback = new Callback(this);
            client = new ClientApp.ServiceReference1.CalculatorClient(new InstanceContext(callback));

        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                this.richTextBox1.Text += "\nCalling WCF service add method... Add(" + this.textBox1.Text + "," + this.textBox2.Text + ") = " + client.Add(Convert.ToDouble(this.textBox1.Text), Convert.ToDouble(this.textBox2.Text)).ToString();
            }
            catch (Exception ex)
            {
                this.richTextBox1.Text = ex.ToString();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            try
            {
                if (client.Subscribe())
                {
                    this.richTextBox1.Text += "\nClient subscribed";
                    isSubscribed = true;
                }
                else
                    this.richTextBox1.Text += "\nCould not subscribe client";
            }
            catch (Exception ex)
            {
                this.richTextBox1.Text += "\n"+ex.ToString();
            }
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            try
            {
                if(isSubscribed)
                MessageBox.Show("Client unsubscribed..."+ client.UnSubscribe());
            }
            catch (Exception ex)
            {
                MessageBox.Show("Could not unsubscribe client");
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            try
            {
                this.richTextBox1.Text += "\nCalling WCF service subtract method... Subtract("+this.textBox1.Text+","+ this.textBox2.Text+") = " + client.Subtract(Convert.ToDouble(this.textBox1.Text), Convert.ToDouble(this.textBox2.Text)).ToString();
            }
            catch (Exception ex)
            {
                this.richTextBox1.Text = ex.ToString();
            }
        }

        private void button4_Click(object sender, EventArgs e)
        {
            try
            {
                this.richTextBox1.Text += "\nCalling WCF service multiply method... Multiply(" + this.textBox1.Text + "," + this.textBox2.Text + ") = " + client.Multiply(Convert.ToDouble(this.textBox1.Text), Convert.ToDouble(this.textBox2.Text)).ToString();
            }
            catch (Exception ex)
            {
                this.richTextBox1.Text = ex.ToString();
            }
        }

        private void button5_Click(object sender, EventArgs e)
        {
            try
            {
                this.richTextBox1.Text += "\nCalling WCF service divide method... Divide(" + this.textBox1.Text + "," + this.textBox2.Text + ") = " + client.Divide(Convert.ToDouble(this.textBox1.Text), Convert.ToDouble(this.textBox2.Text)).ToString();
            }
            catch (Exception ex)
            {
                this.richTextBox1.Text = ex.ToString();
            }
        }

    }
}