/*_________________________________________________________________________________

                             S T R E A M   R E A D E R   /   W R I T E R   D E M O
                                                    Created 11/9/06
                                                        Ron Kessler
                                                    C# 2005 Version
 _________________________________________________________________________________

 Last updated 1/18/07

 FEATURES: 
    1.  Shows how to read/write to a sequential text file
    2.  Lets user create file when program first loads
    3.  Items can be added/removed from list box
    4.  Items in list box can be saved to disk
    5.  Shows how to use Foreach loop with list box items
    6.  Uses structured error handling
 * 7.  I create Stream objects with the new "using" statement borrowed from VB. This creates
 *     the object but when it goes out of scope, it automatically disposes of it!!
*/

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

//---be sure to add this for Stream Classes
using System.IO;

namespace Using_Streams
{
    public partial class frmMain : Form
    {

 
        public frmMain ()
           
        {
            InitializeComponent();
        }

        //---class-level variables
        string diskFile = "..\\..\\inventory.txt";        //our datafile  remember to include the ..\\ bit!
    
        
       
        private void frmMain_Load(object sender, EventArgs e)
        {
            DoReload();
        }

        
       
       
       /// <summary>
       /// This method is called from form_load and reload_click to populate the listbox
       /// </summary>
        private void DoReload()

        {
            
           
            //---if file does not exist lets create it for them if they want to.
            if (File.Exists(diskFile) == false)
            {
                DialogResult button1 = MessageBox.Show(
                "Cannot locate inventory file. Shall I create it?","System Message", 
                MessageBoxButtons.YesNo, MessageBoxIcon.Question);

                if (button1 == DialogResult.Yes)
                    File.Create(diskFile);
                else
                    this.Close();            //close the form
               
            }
            else
            {
                    try
                    {
                        lstItems.Items.Clear();              //no duplicates
                        using (StreamReader myReader = new StreamReader (diskFile))   //this will close/dispose of reader automatically
                        {
                            while (myReader.Peek() != -1) 
                            {
                                string dataFromFile = myReader.ReadLine();
                                lstItems.Items.Add(dataFromFile);

                            }
                            myReader.Close();
                        }
                    }
                    catch (Exception e)
                    {
                    
                       MessageBox.Show("An error occurred while reading...." + e.Message,
                           "System Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                        this.Close();
                    }
            }
             
        }

        private void btnReload_Click(object sender, EventArgs e)
        {
            DoReload();
        }

     
       /// <summary>
       /// Add new item to listbox
       /// </summary>
       /// <param name="sender"></param>
       /// <param name="e"></param>
 
        private void btnAdd_Click(object sender, EventArgs e)
        {
            string myNewItem = txtNewItem.Text.Trim();
            lstItems.Items.Add(myNewItem);
        }

        
       /// <summary>
       /// Update changes to text file
       /// </summary>
       /// <param name="sender"></param>
       /// <param name="e"></param>
        private void btnSave_Click(object sender, EventArgs e)
        {

            try
            {
                using (StreamWriter myWriter = new StreamWriter(diskFile, false))

                    foreach (string myItem in lstItems.Items)
                    {
                        myWriter.WriteLine(myItem);
                    }
                    MessageBox.Show("Your data has been updated.",
                        "System message",MessageBoxButtons.OK,MessageBoxIcon.Information);
            }

            catch (Exception ex)
            {
                MessageBox.Show("I could not save your changes." + ex.Message,
                    "System Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
            
            }

        }
/// <summary>
/// Clear the selected items in list box
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
        private void btnClear_Click (object sender, EventArgs e)
            {
            lstItems.Items.Clear();
            }
/// <summary>
/// Let them confirm a deletion
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
        private void btnDelete_Click (object sender, EventArgs e)
            {

            DialogResult button = MessageBox.Show(
                  "Are you sure you want to delete " + lstItems.SelectedItem + "?", "System Message",
                  MessageBoxButtons.YesNo, MessageBoxIcon.Question);

            if (button == DialogResult.Yes)
                lstItems.Items.Remove(lstItems.SelectedItem);
            else
                txtNewItem.Focus();
          
            }


        private void btnExit_Click (object sender, EventArgs e)
            {
            this.Close();
            }
  
    }

}