Lecture 5:

Structured Variables & File Systems

Checking Variable Range

Enumerations

Structs

Arrays

Enumerations

Structs

Arrays

Specifying an Array

Declaring Jagged Arrays

The Generic List<T>loading data from a file

using System.IO; : :namespace EmpListDemo{ static class Program { static void Main(string[] args) { string fname = "empstable.txt"; string txtline;

List<Employee> Emps = new List<Employee>(); // a generic list of Employee List<Employee> Emps2 = new List<Employee>(); // we will make a copy of Emps // reading employee data from a text file TextReader tr = new StreamReader(fname); do { txtline = tr.ReadLine(); if (txtline == "xxx") break; string[] field = txtline.Split(','); Emps.Add(new Employee(field[0].Trim(),field[1].Trim(), Convert.ToInt32(field[2]), Convert.ToInt32(field[3]), Convert.ToDouble(field[4])));

} while (true); tr.Close(); : :

// display the contents of the list Empsforeach (Employee emp in Emps){ Console.WriteLine("{0} {1} {2} {3} {4}", emp.FirstName, emp.LastName, emp.Age, emp.YrsEmp, emp.Wage);}

Wade Boggs 45 20 12.5Robin Banks 32 13 9.5Jerry Mander 27 6 8.1Amanda Rekonwith 55 25 22.5Doug Wells 38 10 25.05Anita Break 23 2 7.5Juan Abrew 48 7 32.2Ben Dover 37 9 24.15Ilene Dover 28 1 22.9

Displaying the Contents of the List Emps

// we are making a copy of Emps called Emps2foreach (Employee emp in Emps){ Employee emp2 = new Employee(); emp2 = emp; Emps2.Add(emp2);}// so why not just assign one list to the other?// Emps2 = Emps;//// because this would not make a separate copy but// rather point both Emps2 and Emps to the same records!

Making a Copy of a List

// we "tag" each record that passes our criteriaforeach (Employee emp in Emps2){ if (emp.Age > 39 & emp.YrsEmp >= 10) emp.Tag = true;}

// now we remove all records from Emps2 that HAVE NOT // been "tagged" i.e. remove those with emp.Tag = false// this construct is implemented using a delegateEmps2.RemoveAll(delegate(Employee emp){ return !emp.Tag;});

The RemoveAll Delegate Method

age>39 and yrsemp >= 10Wade Boggs 45 20 12.5Amanda Rekonwith 55 25 22.5

Wade Boggs 45 20 12.5Robin Banks 32 13 9.5Jerry Mander 27 6 8.1Amanda Rekonwith 55 25 22.5Doug Wells 38 10 25.05Anita Break 23 2 7.5Juan Abrew 48 7 32.2Ben Dover 37 9 24.15Ilene Dover 28 1 22.9

5 6 4 3 2 7 7 8 6 54 3 2 5 3 2 3 8 8 81 1 2 2 3 3 6 4 5 33 5 5 6 4 9 7 5 2 04 3 8 7 0 4 3 2 5 41 3 2 4 3 5 4 6 5 77 5 6 8 7 7 5 4 7 91 3 2 4 3 6 5 4 3 28 8 9 6 5 5 3 0 0 11 1 1 6 6 8 8 7 6 5

using System.IO;using System.Collections.Generic;using System.Linq;using System.Text;

namespace LoadArrayFromTextfile{ class Program { static void Main(string[] args) { int[,] mat = new int[10,10]; string textline; int k;

TextReader tr = new StreamReader("sample_01.txt"); for (int i = 0; i < 10; i++) { textline = tr.ReadLine(); k = 0; foreach (string str in textline.Split(' ')) { if (str != "") { mat[i, k] = Convert.ToInt32(str); k += 1; } } } tr.Close();

Loading an Array from a Text File

for (int i = 0; i < 10; i++) { for (int j = 0; j < 10; j++) { Console.Write("{0} ", mat[i, j]); } Console.WriteLine(); } Console.ReadKey(); } }}

List<Employee> Emps = new List<Employee>();string txtline;

TextReader tr = new StreamReader("employees.txt");

do{ txtline = tr.ReadLine(); if (txtline == "xxx") break; string[] field = txtline.Split('\t'); Emps.Add(new Employee(field[0].Trim(), field[1].Trim(), Convert.ToInt32(field[2]), Convert.ToInt32(field[3]), Convert.ToDouble(field[4])));

} while (true);tr.Close();

Reading and Writing Textfiles

foreach (Employee emp in Emps){ Console.WriteLine("{0} {1}", emp.FirstName, emp.LastName);}

TextWriter tw = new StreamWriter("employees.txt");foreach (Employee emp in Emps){ tw.WriteLine("{0} \t {1} \t {2} \t {3} \t {4}", emp.FirstName, emp.LastName, emp.Age, emp.YrsEmp, emp.Wage);}tw.WriteLine("xxx");tw.Close();

Reading and Writing Text Filescontinued

Dealing with Datacut & paste

Pasting into Word or PPT Preserves Cells

Pasting to a Text Editor Creates Separators e.g. Tabs

An Example ProjectEmployee Records Manager

Main Form Concept

Defining Test Sets

Incremental Software Development

Messages to User

changed is used to indicate that there is a current edit

alerted is used to indicate that user has been alerted to an issue

saved is used to indicate that the current employess list has been saved to the hard drive

Summary

Type Conversions

Enumerations

Structs

Arrays

String Manipulation

Generic Type List<T>