GUI Windows Form C#

/*
User Interfaces in C#: Windows Forms and Custom Controls
by Matthew MacDonald
Publisher: Apress
ISBN: 1590590457
*/
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
namespace Validation
{
    /// 
    /// Summary description for SimpleValidation.
    /// 

    public class SimpleValidation : System.Windows.Forms.Form
    {
        internal System.Windows.Forms.GroupBox GroupBox1;
        internal System.Windows.Forms.Label Label2;
        internal System.Windows.Forms.Label Label1;
        internal System.Windows.Forms.TextBox txtFirstName;
        internal System.Windows.Forms.TextBox txtLastName;
        internal System.Windows.Forms.Button Button1;
        /// 
        /// Required designer variable.
        /// 

        private System.ComponentModel.Container components = null;
        public SimpleValidation()
        {
            //
            // Required for Windows Form Designer support
            //
            InitializeComponent();
            //
            // TODO: Add any constructor code after InitializeComponent call
            //
        }
        /// 
        /// Clean up any resources being used.
        /// 

        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if(components != null)
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }
        #region Windows Form Designer generated code
        /// 
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// 

        private void InitializeComponent()
        {
            this.GroupBox1 = new System.Windows.Forms.GroupBox();
            this.Label2 = new System.Windows.Forms.Label();
            this.Label1 = new System.Windows.Forms.Label();
            this.txtFirstName = new System.Windows.Forms.TextBox();
            this.txtLastName = new System.Windows.Forms.TextBox();
            this.Button1 = new System.Windows.Forms.Button();
            this.GroupBox1.SuspendLayout();
            this.SuspendLayout();
            // 
            // GroupBox1
            // 
            this.GroupBox1.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                                    this.Label2,
                                                                                    this.Label1,
                                                                                    this.txtFirstName,
                                                                                    this.txtLastName});
            this.GroupBox1.Location = new System.Drawing.Point(8, 12);
            this.GroupBox1.Name = "GroupBox1";
            this.GroupBox1.Size = new System.Drawing.Size(368, 88);
            this.GroupBox1.TabIndex = 11;
            this.GroupBox1.TabStop = false;
            // 
            // Label2
            // 
            this.Label2.Location = new System.Drawing.Point(16, 52);
            this.Label2.Name = "Label2";
            this.Label2.Size = new System.Drawing.Size(64, 16);
            this.Label2.TabIndex = 8;
            this.Label2.Text = "Last Name:";
            // 
            // Label1
            // 
            this.Label1.Location = new System.Drawing.Point(16, 28);
            this.Label1.Name = "Label1";
            this.Label1.Size = new System.Drawing.Size(64, 16);
            this.Label1.TabIndex = 7;
            this.Label1.Text = "First Name:";
            // 
            // txtFirstName
            // 
            this.txtFirstName.Location = new System.Drawing.Point(84, 24);
            this.txtFirstName.Name = "txtFirstName";
            this.txtFirstName.Size = new System.Drawing.Size(152, 21);
            this.txtFirstName.TabIndex = 4;
            this.txtFirstName.Text = "";
            this.txtFirstName.Validating += new System.ComponentModel.CancelEventHandler(this.txtName_Validating);
            // 
            // txtLastName
            // 
            this.txtLastName.Location = new System.Drawing.Point(84, 48);
            this.txtLastName.Name = "txtLastName";
            this.txtLastName.Size = new System.Drawing.Size(152, 21);
            this.txtLastName.TabIndex = 5;
            this.txtLastName.Text = "";
            this.txtLastName.Validating += new System.ComponentModel.CancelEventHandler(this.txtName_Validating);
            // 
            // Button1
            // 
            this.Button1.Location = new System.Drawing.Point(152, 208);
            this.Button1.Name = "Button1";
            this.Button1.Size = new System.Drawing.Size(76, 24);
            this.Button1.TabIndex = 10;
            this.Button1.Text = "OK";
            this.Button1.Click += new System.EventHandler(this.Button1_Click);
            // 
            // SimpleValidation
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 14);
            this.ClientSize = new System.Drawing.Size(384, 242);
            this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                          this.GroupBox1,
                                                                          this.Button1});
            this.Font = new System.Drawing.Font("Tahoma", 8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));
            this.Name = "SimpleValidation";
            this.Text = "SimpleValidation";
            this.GroupBox1.ResumeLayout(false);
            this.ResumeLayout(false);
        }
        #endregion
        private void Button1_Click(object sender, System.EventArgs e)
        {
            this.Close();
        }
        [STAThread]
        static void Main() 
        {
            Application.Run(new SimpleValidation());
        }
        private void txtName_Validating(object sender, System.ComponentModel.CancelEventArgs e)
        {
            if (((TextBox)sender).Text == "")
            {
                MessageBox.Show("You must enter a first and last name.", "Invalid Input", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                e.Cancel = true;
            }
        }
    }
}