at first I am a novice, I am learning is that only two months. (Sorry for my english, I hope u will understand.)
Problem is:
I am trying to create a small database with console application. I have student.csv where are all information about students. When I start application, all informations from this .csv will save into Lists. Like this:
List<Student> zoznam = new List<Student>();
List<string> inicZac = new List<string>();
List<string> ID = new List<string>();
List<string> Meno = new List<string>();
List<string> Priezvisko = new List<string>();
List<string> Adresa = new List<string>();
List<string> DatumNarodenia = new List<string>();
List<string> Heslo = new List<string>();
List<string> Login = new List<string>();
List<string> inicKon = new List<string>();
private int id;
StreamReader reader = new StreamReader(File.OpenRead("student.csv"));
public databazaStudentov()
{
while (!reader.EndOfStream)
{
var line = reader.ReadLine();
var values = line.Split(';');
inicZac.Add(values[0]);
ID.Add(values[1]);
Meno.Add(values[2]);
Priezvisko.Add(values[3]);
Adresa.Add(values[4]);
DatumNarodenia.Add(values[5]);
Heslo.Add(values[6]);
Login.Add(values[7]);
inicKon.Add(values[8]);
zoznam.Add(new Student(values[1], values[2], values[3], values[4], values[5], values[6], values[7]));
}
}
It works good. But now I want secure an easy write into this .csv when I create a new student in a running application.This function is creating a new student:
public void addStudent(string meno, string priezvisko, string adresa, string datum)
{
string tempID = generujID(); //random gener ID
string tempLogin = generujLogin(meno, priezvisko); //random gener Login
string tempHeslo = generujHeslo(); //random gener password
zoznam.Add(new Student(tempID, meno, priezvisko, adresa, datum, tempLogin, tempHeslo));
ID.Add(tempID);
Meno.Add(meno);
Priezvisko.Add(priezvisko);
Adresa.Add(adresa);
DatumNarodenia.Add(datum);
Login.Add(tempLogin);
Heslo.Add(tempHeslo);
// I created a new student and now I want save him into the csv
}
and here is my .csv: http://i.imgur.com/P0PnxpB.jpg?1
There are probably more ways how to fix it. I will be gratefull if someone show me How to save a new student on a new row or How to overwrite with Lists everything in my student.csv . Thanks for tips and sorry for my english.
I would create a new class to create csv file from your student.
public class CsvGen
{
private _fileName=string.Empty;
private StringBuilder csvRows;
public CsvGen(string fileName)
{
_fileName=fileName;
csvRows=new StringBuilder();
}
public void Add(Student student)
{
var row=String.Format("{0},{1},{2},{3}",student.Id,student.Name,student.City,
Environment.NewLine);
csvRows.Append(row);
}
public void SaveFile()
{
System.IO.File.WriteAllText(_fileName,csvRows.ToString());
}
}
Now from your other class, you can create a new instance of this class and call the AddStudent method everytime you add an item to the list and call SaveFile after your loop.
CsvGen csvGen=new CsvGen(#"C:\\temp\myFile.csv");
// ^ any location with proper permission for .net to write files.
public void AddStudent(int id, string name, string city)
{
Student stud=new Student();
stud.Id=id;
stud.Name=name;
stud.City=city;
csvGen.Add(stud);
}
So once you create all students, You may call the SaveFile method to save the csv file
while (!someCondition)
{
AddStudent(2,"scott","detroit");
}
csvGen.SaveFile();
A quick solution for your question.
public void addStudent(string meno, string priezvisko, string adresa, string datum)
{
//your code
//.........
// I created a new student and now I want save him into the csv
using(StreamWriter sw = new StreamWriter("student.csv", true))//true to append after the file
{
sw.WriteLine("{0};{1};{2};{3};{4};{5};{6};",
tempID, meno, priezvisko, adresa, datum, tempLogin, tempHeslo);
sw.Close();
}
}
If you want to read and write csv, then I'd recommend you try the CsvHelper library, as it would be much simpler than the way you're doing it currently.
Related
I am trying to read text file and store the information into the List<>.
So far, I managed to read strings off the file and split it, but having trouble storing the information onto the List<>. Perhaps I am trying to do too many things under one function.
using System.IO;
private void openFileDialog_Click(object sender, EventArgs e)
{
if (myOpenFileDialog.ShowDialog() == DialogResult.OK) ;
using (FileStream fStream = File.OpenRead(myOpenFileDialog.FileName))
{
StreamReader reader;
reader = new StreamReader(fStream);
string line;
while ((line = reader.ReadLine()) != null)
{
string[] playerInfo = line.Split(';');
int ID = int.Parse(playerInfo[0]);
string firstName = playerInfo[1];
string lastName = playerInfo[2];
DateTime dob = DateTime.Parse(playerInfo[3]);
List<Player> players = new List<Player>
players.add(new Player(id, firstName, lastName, dob);
}
}
}
When I check with MessageBox.Show, it comes out with 0 for the amount of lines I have in the file...
Perhaps my list.add code is in wrong place.
Thank you for your help and your time
You're creating a new List every time you're iterating over a new line, that's probably why you're not getting the correct amount of lines.
I also saw you have a few sintax errors in your code, I'll asume that you didn't copy/paste the code directly from the source and that's the reason of those errors (The Add method is in uppercase, and you missed the parentheses when initializing the List)
The working code would be like this:
List<Player> players = new List<Player>();
while ((line = reader.ReadLine()) != null) {
string[] playerInfo = line.Split(';');
int ID = int.Parse(playerInfo[0]);
string firstName = playerInfo[1];
string lastName = playerInfo[2];
DateTime dob = DateTime.Parse(playerInfo[3]);
players.Add(new Player(id, firstName, lastName, dob);
}
If you want to have access to the list more globally you could do it this way:
Let's assume your class name is Sample:
public class Sample {
// Declare the list as a private field
private List<Player> players;
// Constructor - Creates the List instance
public Sample() {
players = new List<Player>();
}
private void openFileDialog_Click(object sender, EventArgs e) {
players.Clear(); //Clears the list
if (myOpenFileDialog.ShowDialog() == DialogResult.OK) ;
using (FileStream fStream = File.OpenRead(myOpenFileDialog.FileName)) {
StreamReader reader;
reader = new StreamReader(fStream);
string line;
while ((line = reader.ReadLine()) != null) {
string[] playerInfo = line.Split(';');
int ID = int.Parse(playerInfo[0]);
string firstName = playerInfo[1];
string lastName = playerInfo[2];
DateTime dob = DateTime.Parse(playerInfo[3]);
players.Add(new Player(id, firstName, lastName, dob);
}
}
}
}
Declaring the list this way you'll be able to get the values of the list from other methods inside the same class.
I have a list of strings which holds file paths.
List<string> allFilesWithPathList = new List<string>();
allFilesWithPathList.Add(#"G:\Test\A.sql");
allFilesWithPathList.Add(#"G:\Test\B.sql");
allFilesWithPathList.Add(#"G:\Test\C.sql");
return allFilesWithPathList;
I have another list which holds a subset of files – but it has only the file name; not the path.
List<string> excludeList = new List<string>();
excludeList.Add("B.sql");
Now I need to get files from allFilesWithPathList that is not present in excludeList. Currently I am doing the following, using EXCEPT, after creating another list with file names only.
List<string> allFileNamesOnlyList = new List<string>();
foreach (string fileNameWithPath in allFilesWithPathList)
{
//Remove path and get only file name
int pos = fileNameWithPath.LastIndexOf(#"\") + 1;
string value = fileNameWithPath.Substring(pos, fileNameWithPath.Length - pos);
allFileNamesOnlyList.Add(value);
}
//EXCEPT logic
List<string> eligibleListToProcess = allFileNamesOnlyList.Except(excludeList).ToList();
What is the best way in LINQ to get this logic working without introducing another list like the above?
Note: I am using .Net 4.5
Complete code
class Program
{
static void Main(string[] args)
{
List<string> allFilesWithPathList = GetAllFilesWithPath();
List<string> excludeList = new List<string>();
excludeList.Add("B.sql");
List<string> allFileNamesOnlyList = new List<string>();
foreach (string fileNameWithPath in allFilesWithPathList)
{
//Remove path and get only file name
int pos = fileNameWithPath.LastIndexOf(#"\") + 1;
string value = fileNameWithPath.Substring(pos, fileNameWithPath.Length - pos);
allFileNamesOnlyList.Add(value);
}
//EXCEPT logic
List<string> eligibleListToProcess = allFileNamesOnlyList.Except(excludeList).ToList();
//Print all eligible files
foreach (string s in eligibleListToProcess)
{
Console.WriteLine(s);
}
Console.ReadLine();
}
public static List<string> GetAllFilesWithPath()
{
List<string> allFilesWithPathList = new List<string>();
allFilesWithPathList.Add(#"G:\Test\A.sql");
allFilesWithPathList.Add(#"G:\Test\B.sql");
allFilesWithPathList.Add(#"G:\Test\C.sql");
return allFilesWithPathList;
}
}
allFilesWithPathList.Where(path => !allFileNamesOnlyList.Contains(Path.GetFileName(path));
There are two improvements here.
Path.GetFileName is much better than splitting the path yourself.
IEnumerable.Where in conjunction with ICollection.Contains to actually query the list in a succinct and easy to read way.
This should work
allFilesWithPathList.Where(x => !excludeList.Any(y => x.EndsWith(y)))
Background on this project. It started as a simple homework assignment that required me to store 5 zip codes and their corresponding cities. When a user puts a Zip code in a textbox, a corresponding city is returned, and likewise the opposite can be done. I wrote the code to return these values, but then I decided I wanted to store ALL zip codes and their corresponding Cities in an external .csv, and store those values in arrays and run the code off that because if its worth doing, its worth overdoing! To clarify, this is no longer for homework, just to learn more about using external files in C#.
In the following code, I have called to open the file successfully, now I just need help in figuring out how to pull the data that is stored in two separate columns (one for city, one for zip code) and store them in two arrays to be acted upon by the for loop. Here is the code I have now. You can see how I have previously stored the other values in arrays and pulled them out:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btnConvert2City_Click(object sender, EventArgs e)
{
try
{
string dir = System.IO.Path.GetDirectoryName(
System.Reflection.Assembly.GetExecutingAssembly().Location);
string path = dir + #"\zip_code_database_edited.csv";
var open = new StreamReader(File.OpenRead(path));
int EnteredZipcode = Convert.ToInt32(txtZipcode.Text.Trim());
string result = "No Cities Found";
string[] Cities = new String[5] { "FLINTSTONE", "JAMAICA", "SCHENECTADY", "COTTONDALE", "CINCINNATI" };
int[] Zipcode = new int[5] { 30725, 11432, 12345, 35453, 45263 };
for (int i = 0; i <= Zipcode.Length - 1; i++)
{
if (Zipcode[i] == EnteredZipcode)
{
result = Cities[i];
break;
}
}
string DisplayState = result;
txtCity.Text = DisplayState;
}
catch (FormatException)
{
MessageBox.Show("Input must be numeric value.");
}
catch (OverflowException)
{
MessageBox.Show("Zipcode to long. Please Re-enter");
}
}
private void btnConvert2Zipcode_Click(object sender, EventArgs e)
{
string dir = System.IO.Path.GetDirectoryName(
System.Reflection.Assembly.GetExecutingAssembly().Location);
string path = dir + #"\zip_code_database_edited.csv";
var open = new StreamReader(File.OpenRead(path));
String EnteredCity = txtCity.Text.ToUpper();
string result = "No Zipcode Found";
string[] Cities = new String[5] { "FLINTSTONE", "JAMAICA", "SCHENECTADY", "COTTONDALE", "CINCINNATI" };
int[] Zipcode = new int[5] { 30725, 11432, 12345, 35453, 45263 };
for (int i = 0; i <= Cities.Length - 1; i++)
{
if (Cities[i] == EnteredCity)
{
result = Convert.ToString(Zipcode[i]);
break;
}
}
string DisplayZip = result;
txtZipcode.Text = DisplayZip;
}
}
The following data is a snippet of what the data in my excel .csv looks like:
zip,primary_city
44273,Seville
44274,Sharon Center
44275,Spencer
44276,Sterling
44278,Tallmadge
44280,Valley City
44281,Wadsworth
44282,Wadsworth
44285,Wayland
And so on for about 46,000 rows.
How can I pull the zip and the primary_city into two separate arrays (I'm guessing with some ".Split "," "line) that my for-loop can operate on?
Also, if there are better ways to go about this, please let me know (but be sure to leave an explanation as I want to understand where you are coming from).
Don't create two separate array.Create a separate class for city
class City
{
public string Name{get;set;}
public int ZipCode{get;set;}
}
Now to read the data from that csv file
List<City> cities=File.ReadAllLines(path)
.Select(x=>new City
{
ZipCode=int.Parse(x.Split(',')[0]),
Name=x.Split(',')[1]
}).ToList<City>();
Or you can do this
List<City> cities=new List<City>();
foreach(String s in File.ReadAllLines(path))
{
City temp=new City();
temp.ZipCode=int.Parse(s.Split(',')[0]);
temp.Name=s.Split(',')[1];
cities.Add(temp);
}
You can try this:
string dir = System.IO.Path.GetDirectoryName(
System.Reflection.Assembly.GetExecutingAssembly().Location);
string path = dir + #"\zip_code_database_edited.csv";
var open = new StreamReader(File.OpenRead(path));
var cities = new HashList<string>();
var zipCodes = new HashList<int>();
var zipAndCity = new string[2];
string line = string.Empty;
using (open)
{
while ((line = reader.ReadLine()) != null)
{
zipAndCity = line.Split(",");
zipCodes.Add(int.Parse(zipAndCity[0]));
cities.Add(zipAndCity[1]);
}
}
I am posting this answer having learned much more about C# since I posted this question. When reading a CSV, there are better options than String.Split().
The .NET Framework already has a built-in dedicated CSV parser called TextFieldParser.
It's located in the Microsoft.VisualBasic.FileIO namespace.
Not only are there many edge cases that String.Split() is not properly equipped to handle, but it's also much slower to use StreamReader.
I retrieved a list of users from database, something like
List<User> users = <..list of users from db...>
Name, LastName, DateOfBirth //multidimensional array??
Now I want to store this list as a string and I want be able to reuse it i.e.
string strUsers = users.ToArray().ToString();
How to recreate a list of users from strUsers?
Is it possible?
Use the string.Join method, e.g.
var joined = string.Join(",", users.Select(u => u.Name));
This would give you a single string of user's names separated by ','.
Or for multiple columns:
var joined = string.Join(",",
users.Select(u => u.FirstName + " " + u.LastName ));
You can reverse the process using string.Split, e.g.
var split = joined.Split( new [] {','} );
If you have a lot of users and a lot of columns, it would be better to write your own custom converter class.
public static class UsersConverter
{
// Separates user properties.
private const char UserDataSeparator = ',';
// Separates users in the list.
private const char UsersSeparator = ';';
public static string ConvertListToString(IEnumerable<User> usersList)
{
var stringBuilder = new StringBuilder();
// Build the users string.
foreach (User user in usersList)
{
stringBuilder.Append(user.Name);
stringBuilder.Append(UserDataSeparator);
stringBuilder.Append(user.Age);
stringBuilder.Append(UsersSeparator);
}
// Remove trailing separator.
stringBuilder.Remove(stringBuilder.Length - 1, 1);
return stringBuilder.ToString();
}
public static List<User> ParseStringToList(string usersString)
{
// Check that passed argument is not null.
if (usersString == null) throw new ArgumentNullException("usersString");
var result = new List<User>();
string[] userDatas = usersString.Split(UsersSeparator);
foreach (string[] userData in userDatas.Select(x => x.Split(UserDataSeparator)))
{
// Check that user data contains enough arguments.
if (userData.Length < 2) throw new ArgumentException("Users string contains invalid data.");
string name = userData[0];
int age;
// Try parsing age.
if (!int.TryParse(userData[1], out age))
{
throw new ArgumentException("Users string contains invalid data.");
}
// Add to result list.
result.Add(new User { Name = name, Age = age });
}
return result;
}
}
You will win performance wise using the StringBuilder to build up your users string. You could also easily expand the converter to take account different separators/additional logic etc.
If you need a more generic solution (to be able to use for any class), you could create a converter which uses reflection to iterate over all the public fields, get/set properties to see what can be extracted as string and later reverse the process to convert your string back to the list.
I think what you're looking for is something that lets you dump all users to a string and get the users back from the string, correct?
I suggest something like this:
Add a method that returns an XElement to the Users type:
public XElement GetXElement()
{
return new XElement("User", new XElement("Name", this.FirstName)) //and so on...
}
and then one that decodes the string into a user:
static User GetUserFromXElement(string xml)
{
XElement temp = XElement.Parse(xml);
User temp = new User();
foreach (XElement inner in temp.Elements())
{
switch inner.Name
{
case "Name":
temp.Name = inner.Value
break;
//whatever
}
}
}
And then do this:
public string UsersToElements (List<Users> toWrite)
{
Stringbuilder sb = new StringBuilder();
StringWriter sw = new StringWriter(sb);
XElement root = new XElement("root");
XDocument temp = new XDocument(root);
foreach (User user in toWrite)
{
root.Append(user.GetXElement());
}
temp.Save(sw);
return sw.ToString();
}
and this:
public List<Users> ElementsToUsers (string xml)
{
List<Users> usrsList = new List<Users>();
XDocument temp = XDocument.Load(xml);
foreach (XElement e in XDocument.Root.Elements())
{
usrsList.Append(Users.GetUserFromXElement(e));
}
return usrsList;
}
JSON solution (using JSON.NET)
public JObject GetJObject()
{
return new JObject("user", new JProperty("name", this.FirstName)); //so on
}
static User GetUserFromJObject(string json)
{
JObject obj = JObject.Parse(json);
return new User() { FirstName = (string)obj["user"]["name"] }; //so on
}
public string UsersToElements (List<Users> users)
{
JObject root = new JObject(from usr in users select new JAttribute("user", usr.GetJObject());
return root.ToString();
}
public List<users> ElementsToUsers(string json)
{
List<Users> users = new List<Users>();
JObject temp = JObject.Parse(json);
foreach (JObject o in (JEnumerable<JObject>)temp.Children())
{
users.Add(Users.GetUserFromJObject(o.ToString());
}
return users;
}
I have no idea if ths works :/ (well the XML I know it does, not so sure about the JSON)
Use this code
string combindedString = string.Join( ",", myList );
var Array = combindedString.Split( new [] {','} );
I have a flat text file that contains the following data;
Following are the names and ages in a text file.
26|Rachel
29|Chris
26|Nathan
The data is kept on a server (e.g http://domain.com/info.dat), I'd like to read this text file and insert it into an array (age and name). I'd like to ignore the first line (Following are....).
I've sorted the code to grab the data file using a webclient and the code to open the dat file using streamreader as follows;
using (StreamReader sr = new StreamReader(path))
{
while (sr.Peek() >= 0)
{
string[] channels = Text.Split('|');
foreach (string s in channels)
{
}
}
}
The problem with the above code is when it comes to inputting it into an array with the correct columns. Could anyone give me some pointers?
Many thanks
How about an answer that uses some LINQ:
var results = from str in File.ReadAllLines(path).Skip(1)
where !String.IsNullOrEmpty(str)
let data = str.Split('|')
where data.Length == 2
select new Person { Age = Int32.Parse(data[0], NumberStyles.Integer, CultureInfo.CurrentCulture), Name = data[1] };
results is now IEnumerable<Person> which you can do ToList or ToArray on to get a List<Person> or Person[], or you can simply use the results with a foreach loop.
UPDATE: here is the Person class needed to make this more functional.
public class Person
{
public int Age { get; set; }
public string Name { get; set; }
}
You could do something like this. (There is no error checking, you might want to check for errors when parsing the age etc.
class Person
{
string Name {get;set;}
int Age {get;set;}
}
List<Person> people = new List<Person>();
string line;
using (StreamReader sr = new StreamReader(path))
{
sr.ReadLine();
while ((line == sr.ReadLine()) != null)
{
string[] channels = line.Split('|');
people.Add(new Person() {Age=int.Parse(channels[0]), Name=channels[1]});
}
}
You should use Dictionary and not Array to store the data.
Sample code:
FileStream fs = new FileStream("filename");
Dictionary<int,string> dict = new Dictionary<int,string>();
string line = "";
fs.ReadLine(); //skip the first line
while( (line = fs.ReadLine()) != null)
{
string parts = line.split("|".ToCharArray());
dict.Add(int.Parse(parts[0]), parts[1]);
}