Develop Reference

Can't append a list to an existing file

I have an existing .txt file that I would like to use to store my data, but when using this code I get an error at line 39 at switch case 1.
using System;
using System.Collections.Generic;
using System.IO;
class Program
{
public static List<Pw> Site = new List<Pw>();
static void Main(string[] args)
{
string file = #"C: \Users\james\Documents\DataFolder\Vault.txt";
string command = "";
while (command != "exit")
{
Console.Clear();
Console.WriteLine("Please enter a command: ");
command = Console.ReadLine().ToLower();
switch (command)
{
case "1":
AddPw();
File.AppendAllLines(file, Pw.Site);
break;
case "2":
if (File.Exists(file))
{
// Read all the content in one string
// and display the string
string str = File.ReadAllText(file);
Console.WriteLine(str);
}
break;
}
}
}
private static void AddPw()
{
Pw pw = new Pw();
Console.Write("Enter the Username/Email: ");
pw.Username = Console.ReadLine();
Console.Write("Enter Full Name: ");
pw.FullName = Console.ReadLine();
Console.Write("Enter Phone Number: ");
pw.PhoneNumber = Console.ReadLine();
Console.Write("Enter Your Password: ");
string password = Console.ReadLine();
pw.Password = password;
Site.Add(pw);
}
private static void PrintPw(Pw pw)
{
Console.WriteLine("Username/Email: " + pw.Username);
Console.WriteLine("Full Name: " + pw.FullName);
Console.WriteLine("Phone Number: " + pw.PhoneNumber);
Console.WriteLine("Password: " + pw.Password[0]);
Console.WriteLine("-------------------------------------------");
}
private static void ListPw()
{
if (Site.Count == 0)
{
Console.WriteLine("Your address book is empty. Press any key to continue.");
Console.ReadKey();
return;
}
Console.WriteLine("Here are the current people in your address book:\n");
foreach (var pw in Site)
{
PrintPw(pw);
}
Console.WriteLine("\nPress any key to continue.");
Console.ReadKey();
}
}
public class Pw
{
public string Username { get; set; }
public string FullName { get; set; }
public string PhoneNumber { get; set; }
public string Password { get; set; }
}

I have updated your existing function.
using this function you can add and append data in existing file.
private static void AddPw(string filePath)
{
try
{
Pw pw = new Pw();
if (!File.Exists(filePath))
{
using (System.IO.StreamWriter sw = new System.IO.StreamWriter(filePath))
{
Console.Write("Enter the Username/Email: ");
pw.Username = Console.ReadLine();
sw.WriteLine(pw.Username);
Console.Write("Enter Full Name: ");
pw.FullName = Console.ReadLine();
sw.WriteLine(pw.FullName);
Console.Write("Enter Phone Number: ");
pw.PhoneNumber = Console.ReadLine();
sw.WriteLine(pw.PhoneNumber);
Console.Write("Enter Your Password: ");
pw.Password = Console.ReadLine();
sw.WriteLine(pw.Password);
}
}
else
{
using (StreamWriter sw = File.AppendText(filePath))
{
Console.Write("Enter the Username/Email: ");
pw.Username = Console.ReadLine();
sw.WriteLine(pw.Username);
Console.Write("Enter Full Name: ");
pw.FullName = Console.ReadLine();
sw.WriteLine(pw.FullName);
Console.Write("Enter Phone Number: ");
pw.PhoneNumber = Console.ReadLine();
sw.WriteLine(pw.PhoneNumber);
Console.Write("Enter Your Password: ");
pw.Password = Console.ReadLine();
sw.WriteLine(pw.Password);
}
}
}
catch (Exception ex)
{
}
}

File.AppendAllLines(file, Pw.Site);
In this line, you need to pass an IEnumerable for AppendAllLines to work. You can easily convert Site (which is List<Pw>) to an IEnumerable<string> using the ConvertAll method. Here's one way of achieving this:
Replace that line with this:
File.AppendAllLines(file, Site.ConvertAll<string>(
(p) => string.Format("{0} | {1} | {2} | {3}\n",
p.Username,
p.FullName,
p.PhoneNumber,
p.Password
))
);
This "lambda" basically takes your Pw object and converts it into a string inline.

Read 2 lines by 2lines in textfile

Suppose that the method ReadUser below is reading the user and password in the textfile. The problem is, it doesn't read the rest of the textfile after reading the first 2 lines. How to solve this issue?
*Edit: how do I read first 2 lines then another 2 lines in the textfile ?
public override void ReadUser()
{
user = base.UserID;
password = base.Password;
using (StreamReader sr = new StreamReader(File.Open("C:\\Users\\user\\Documents\\Projects\\AdministratorModule//userTextFile.txt", FileMode.Open)))
{
user1 = sr.ReadLine();
password1 = sr.ReadLine();
sr.Close();
if (user == user1 && password == password1)
{
Console.WriteLine("Login Successfull");
}
else
{
Console.WriteLine("Login Failed");
}
}
}

simple a basic logic
int currentLine = 0;
//no need use close method with using
using (StreamReader sr = new StreamReader(File.Open("C:\\Users\\user\\Documents\\Projects\\AdministratorModule//userTextFile.txt", FileMode.Open)))
{
string line;
while ((line = sr.ReadLine()) != null)
{
switch (++currentLine)
{
case 1: user1 = line; break;
case 2: password1 = line; break;
case 3: otherVariable = line; break;
case 4: yetAnotherVariable = line; break;
......
}
//rest of your logic
}
}
However, if for some reason you need to store all the strings in an array, you're best off just using File.ReadAllLines();

Reading doubles from a .txt file and copying them to a new .txt file (Streamreader/Streamwriter)

static void Main(string[] args)
{
Console.Write("Enter the name of the file to open: ");
string input = Console.ReadLine();
Console.Write("Enter the name of the output file: ");
string output = Console.ReadLine();
var InFile = new StreamReader(input);
int TotalD = 0;
StreamWriter OutFile = new StreamWriter(output);
Console.WriteLine();
try
{
using (InFile)
{
double DInput = 0;
while (DInput == double.Parse(InFile.ReadLine()))
{
while (!InFile.EndOfStream)
{
DInput = double.Parse(InFile.ReadLine());
double DOutput = DInput * 2;
InFile.Close();
using (OutFile)
{
OutFile.WriteLine(DOutput);
}
}
InFile.Close();
}
}
using (StreamReader r = new StreamReader(input))
{
TotalD = 0;
while (r.ReadLine() != null) { TotalD++; }
}
}
catch (IOException Except)
{
Console.WriteLine(Except.Message);
}
Console.WriteLine("There were {0} doubles copied to {1}.", TotalD, output);
Console.WriteLine();
Console.Write("Press <enter> to exit the program: ");
Console.Read();
}
Ok so I've asked this question before but the problem was that I didn't know the input.txt file had to be manually written instead of generated like I was doing before. This current version also runs without error messages. The only issue now is that output.txt is completely blank. Any help would be much appreciated!
The idea of this project is to read the doubles from input.txt:
1.5
2.3
3
4.7
5
And write them to output.txt only times 2:
3.0
4.6
6
9.4
10

string input = #"C:\temp\testinput.txt";
string output = #"C:\temp\testoutput.txt";
using (var reader = new StreamReader(input))
{
using (var writer = new StreamWriter(output))
{
var line = reader.ReadLine();
while (line != null)
{
var value = float.Parse(line);
var result = value * 2;
writer.WriteLine(result);
line = reader.ReadLine();
}
}
}
Format the output to the file so it looks like what you want.

windows forms array to file

Newbie here, currently studying C# course and totally new to coding and stuff.
Sorry if this question is already been asked, I've been googling for quite some time and still unable to find a proper answer or anything near it.
Question being simple. I have an array that contains string needs to be saved onto a file, needs to be retrieved when required.
example
string[] item_name = {"abc", "def", "ghi"};
float[] item_cost = {30f,20f,10f};
int[] item_qty = {10,20,30};
How do i go about saving all these data into a file (e.g .txt) and then retrieve at a button_click command?

try this.... u will get answer....
static void Main(string[] args)
{
while (true)
{
Console.WriteLine("Select your option: 1 for Write, 2 for Read, 3 for Search, others for exit");
int flag = Convert.ToInt32(Console.ReadLine());
if (flag != 1 && flag != 2 && flag != 3) break;
switch (flag)
{
case 1:
{
StreamWriter SW = new StreamWriter(#"C:\test.txt");
while (true)
{
Console.WriteLine("Enter some value for inset into text file, 0 for exit\n");
string temp = Console.ReadLine();
if (temp != "0")
{
SW.WriteLine(temp);
}
else
{
break;
}
}
//SW.Dispose();
SW.Close();
break;
}
case 2:
{
StreamReader SR = new StreamReader(#"C:\test.txt");
while (true)
{
Console.WriteLine(SR.ReadLine());
if (SR.EndOfStream == true)
break;
}
SR.Dispose();
SR.Close();
break;
}
case 3:
{
Console.Write("entre ur value:\t");
string value = Console.ReadLine();
StreamReader SR = new StreamReader(#"C:\test.txt");
bool flg = false;
while (true)
{
if (value == SR.ReadLine())
{
Console.WriteLine(value + " was found in ur text");
flg = true;
break;
}
if (SR.EndOfStream == true)
break;
}
if (flg != true)
{
Console.WriteLine("Sorry not found");
}
SR.Dispose();
SR.Close();
break;
}
default:
{
break;
}
}
}
}

Create a stream reader in c# console to read only one student at a time instead of all of them using a .txt file

class Program
{
static string strFile = "Student Database.txt";
static void Main(string[] args)
{
string strInput = null; // user input string
start:
System.IO.DirectoryInfo dir = new DirectoryInfo("student_results.txt");
// Request user input as to actions to be carried out
Console.WriteLine("\nWhat do you want to do?\n" +
" 1.View Student(s)\n 2.Add a New Student\n 3.Exit program");
// Save user input to make decision on program operation
strInput = Console.ReadLine();
// Switch statement checking the saved user input to decide the action
// to be carried out
switch (strInput)
{
case "1": // choice for view file
Console.Clear();
string file = AppDomain.CurrentDomain.BaseDirectory +
#"student_results.txt";
StreamReader sr = new StreamReader(file);
string wholeFile = sr.ReadToEnd();
Console.Write(wholeFile + "");
sr.Close();
goto start;
...
}
...
}
...
}
I want this part of my code to just read the students indivially and relay them back to me, instead of how it is doing so at the moment were it just calls all of them back to me when I press '1) view Student' it pretty much says "please enter the students name or ID number of which student you would like to view".
I've currently have got the ID number running off a random number generator.
Thank you for your time guys.

Welcome to SO, first of all goto is not a good choice in C# in 99% of cases, and you'd better use loops. For your code I would save each student in a single line and at the time of reading students I would read them line by line untill I found the student.
class Program
{
static string strFile = "Student Database.txt";
static void Main(string[] args)
{
string strInput = ""; // user input string
while (strInput != "3")
{
System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo("student_results.txt");
Console.WriteLine("\nWhat do you want to do?\n 1.View Student(s)\n 2.Add a New Student\n 3.Exit program"); // request user input as to actions to be carried out
strInput = Console.ReadLine(); //save user input to make decision on program operation
switch (strInput)
{
case "1":
Console.Clear();
Console.WriteLine("Enter Student ID: \n");
string file = AppDomain.CurrentDomain.BaseDirectory + #"student_results.txt";
StreamReader sr = new StreamReader(file);
string StudentID = Console.ReadLine();
string line = "";
bool found = false;
while((line = sr.ReadLine()) != null)
{
if (line.Split(',')[0] == StudentID)
{
found = true;
Console.WriteLine(line);
break;
}
}
sr.Close();
if (!found)
{
Console.WriteLine("Not Found");
}
Console.WriteLine("Press a key to continue...");
Console.ReadLine();
break;
case "2":
Console.WriteLine("Enter Student ID : ");
string SID = Console.ReadLine();
Console.WriteLine("Enter Student Name : ");
string SName = Console.ReadLine();
Console.WriteLine("Enter Student Average : ");
string average = Console.ReadLine();
string wLine = SID + "," +SName+":"+average;
file = AppDomain.CurrentDomain.BaseDirectory + #"student_results.txt";
StreamWriter sw = File.Exists(file) ? File.AppendText(file) : new StreamWriter(file);
sw.WriteLine(wLine);
sw.Close();
Console.WriteLine("Student saved on file, press a key to continue ...");
Console.ReadLine();
Console.Clear();
break;
case "3":
return;
default:
Console.Clear();
Console.WriteLine("Invalid Command!\n");
break;
}
}
}
}
this code might not be complete, I wanted to give you the idea, I hope it helps.

Presuming you are not dealing with a huge file of students, and on the basis that you want to make multiple queries, i would not read the text file line by line each time.
Instead create a student class, read the file once on init, and create a list< student > from the data. Then you can query it with LinQ

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
namespace ReadStudents
{
class Program
{
static string _filename = "students.txt";
static void Main(string[] args)
{
List<Student> students = new List<Student>();
// Load students.
StreamReader reader = new StreamReader(_filename);
while (!reader.EndOfStream)
students.Add( new Student( reader.ReadLine()));
reader.Close();
string action;
bool showAgain = true;
do
{
Console.WriteLine("");
Console.WriteLine("1. See all students.");
Console.WriteLine("2. See student by ID.");
Console.WriteLine("3. Add new student.");
Console.WriteLine("0. Exit.");
Console.WriteLine("");
action = Console.ReadLine();
switch (action)
{
case "1":
foreach (Student item in students)
item.Show();
break;
case "2":
Console.Write("ID = ");
int id = int.Parse( Console.ReadLine() ); // TODO: is valid int?
foreach (Student item in students)
if (item.Id == id)
item.Show();
break;
case "3":
Console.WriteLine("ID-Name");
Student newStudent = new Student(Console.ReadLine());
students.Add(newStudent);
StreamWriter writer = new StreamWriter(_filename, true);
writer.WriteLine(newStudent);
writer.Close();
break;
case "0":
Console.WriteLine("Bye!");
showAgain = false;
break;
default:
Console.WriteLine("Wrong action!");
break;
}
}
while (showAgain);
}
}
class Student
{
public int Id;
public string Name;
public Student(string line)
{
string[] fields = line.Split('-');
Id = int.Parse(fields[0]);
Name = fields[1];
}
public void Show()
{
Console.WriteLine(Id + ". " + Name);
}
}
}
I assume your data are in "ID-Name" format for example:
1-Alexander
2-Brian
3-Christian
I load file line-by-line and pass to Student class which converts in constructor text data to more friendly form. Next, application shows interface until user write "0".