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CS11ex File Processing Example |
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CS11ex File Processing Example |
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This project is used in class to demonstrate file processing. Creating and submitting the project
is not required, but students may download and expand the self-extracting CS11ex archive into their own workspace if they like.
The data file Coffee.txt is stored in the default folder, which is
in the project's Debug folder within the bin folder.
Folder path: CS11ex > bin > Debug
The interface is the same as CS10ex Loops and Printing, except that
the Save option has been added to the File menu list.
CS11ex Sample Form:
CS11exForm.cs Source Code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.IO; //need this for FileStream, StreamReader, StreamWriter
/*
CS11ex Juan Marquez - portion of example from Bradley 2003
Programmer: Badley/Millspaugh (Marquez CS11ex)
Date: June 2003
Description: Load and Save a list of coffee flavors from a file.
Maintain a list of coffee flavors;
Print a list of all of the coffee flavors.
*/
namespace CS11ex
{
public partial class CS11exForm : Form
{
//Use a flag to track if the data has been changed but not saved
//Set to true as the default; set to false when the user makes a change
private bool cblnIsDataSaved = true;
public CS11exForm()
{
InitializeComponent();
}
private void CS11exForm_Load(object sender, EventArgs e)
{
//This method is automatically executed when the form is loaded
//Load the list box with the data stored in the file
string strFlavorName;
try
{
FileStream flavorsFileIn = new FileStream("Coffees.txt", FileMode.Open);
StreamReader flavorsStreamReader = new StreamReader(flavorsFileIn);
while (flavorsStreamReader.Peek() != -1)
{
strFlavorName = flavorsStreamReader.ReadLine();
cboCoffee.Items.Add(strFlavorName);
}
flavorsStreamReader.Close();
}
catch
{
DialogResult responseDialogResult;
responseDialogResult = MessageBox.Show("Create a new file?",
"File not Found", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
if (responseDialogResult != DialogResult.Yes)
{
this.Close(); //Exit the program
}
}
}
private void CS11exForm_FormClosing(object sender, FormClosingEventArgs e)
{
//After writing this method to handle the FormClosing event, its needs to
//be assigned as the form's FormClosing event handler while in Design Mode.
//After assigning it to the form, the method is automatically executed
//when the form is instructed to close.
//If changes have not been saved, ask user if they want to save the changes
DialogResult responseDialogResult;
if (cblnIsDataSaved == false)
{
responseDialogResult = MessageBox.Show("Coffee list has changed. Save the list?",
"Coffee List Changed", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);
if (responseDialogResult == DialogResult.Yes)
{
mnuFileSave_Click(mnuFileSave, new System.EventArgs());
}
if (responseDialogResult == DialogResult.Cancel)
{
e.Cancel = true; //cancel close event
}
}
}
private void mnuFileSave_Click(object sender, EventArgs e)
{
int intIndex, intMaximum;
try
{
FileStream flavorsFileOut = new FileStream("Coffees.txt", FileMode.Create);
StreamWriter flavorsStreamWriter = new StreamWriter(flavorsFileOut);
intMaximum = cboCoffee.Items.Count;
for (intIndex = 0; intIndex < intMaximum; intIndex++)
{
flavorsStreamWriter.WriteLine(cboCoffee.Items[intIndex]);
}
flavorsStreamWriter.Close();
cblnIsDataSaved = true; //reset flag after saving data
}
catch
{
MessageBox.Show("Error saving the changes to the data file.",
"Error Saving Data", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
//Set cblnIsDataSaved = false when list is changed.
//However, the statement is inside the if statements because
//that's when we know changes have been succesfully made.
private void mnuEditAdd_Click(object sender, EventArgs e)
{
//Add a new coffee flavor to the coffee list
if (cboCoffee.Text != "")
{
cboCoffee.Items.Add(cboCoffee.Text);
cboCoffee.Text = "";
cblnIsDataSaved = false;
}
else
{
MessageBox.Show("Enter a coffee flavor to add", "Missing data",
MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
cboCoffee.Focus();
}
private void mnuEditRemove_Click(object sender, EventArgs e)
{
//Remove the selected coffee from list
if (cboCoffee.SelectedIndex != -1)
{
cboCoffee.Items.RemoveAt(cboCoffee.SelectedIndex);
cblnIsDataSaved = false;
}
else
{
MessageBox.Show("First select the coffee to remove",
"No selection made", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
}
private void mnuEditClear_Click(object sender, EventArgs e)
{
//Clear the coffee list
DialogResult responseDialogResult;
responseDialogResult = MessageBox.Show("Clear the coffee flavor list?",
"Clear coffee list", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
if (responseDialogResult == DialogResult.Yes)
{
cboCoffee.Items.Clear();
cblnIsDataSaved = false;
}
}
private void mnuEditDisplayCount_Click(object sender, EventArgs e)
{
//Display a count of the coffees in list
MessageBox.Show("The number of coffee types is " + cboCoffee.Items.Count.ToString());
}
private void mnuHelpAbout_Click(object sender, EventArgs e)
{
//Create an instance and display AboutForm
AboutForm frmAbout = new AboutForm();
frmAbout.Show();
}
private void mnuFilePrintPreview_Click(object sender, EventArgs e)
{
//Begin print preview by assigning PrintDocument
printPreviewDialog1.Document = printDocument1;
printPreviewDialog1.ShowDialog();
}
private void mnuFilePrint_Click(object sender, EventArgs e)
{
//Trigger the print process by calling the Print method
printDocument1.Print();
}
private void printDocument1_PrintPage(object sender,
System.Drawing.Printing.PrintPageEventArgs e)
{
//Handle printing and print previews
//printPreviewDialog1.ShowDialog() and printDocument1.Print() trigger
// PrintPage event.
Font printFont = new Font("Arial", 12);
Font headingFont = new Font("Arial", 14, FontStyle.Bold);
float fltLineHeight = printFont.GetHeight();
float fltPrintX = e.MarginBounds.Left;
float fltPrintY = e.MarginBounds.Top;
string strPrintLine;
//Print Headings
strPrintLine = "Coffee List ";
e.Graphics.DrawString(strPrintLine, headingFont,
Brushes.Black, fltPrintX, fltPrintY);
strPrintLine = "by Programmer Name";
fltPrintY += fltLineHeight;
e.Graphics.DrawString(strPrintLine, headingFont,
Brushes.Black, fltPrintX, fltPrintY);
//Leave a blank line between heading and detail line
fltPrintY += fltLineHeight * 2;
//Loop through the entire list
for (int intIndex = 0; intIndex <= cboCoffee.Items.Count - 1; intIndex++)
{
//Set up a line
strPrintLine = cboCoffee.Items[intIndex].ToString();
//Send the line to the graphics page object
e.Graphics.DrawString(strPrintLine, printFont,
Brushes.Black, fltPrintX, fltPrintY);
//Increment the Y position for the next line
fltPrintY += fltLineHeight;
}
}
private void mnuFileExit_Click(object sender, EventArgs e)
{
this.Close();
}
}
}