Develop Reference

How to read binary files until EOF in C#

I have a function to write some data into a binary file
private void writeToBinFile (List<MyClass> myObjList, string filePath)
{
FileStream fs = new FileStream(filePath, FileMode.Create);
BinaryWriter bw = new BinaryWriter(fs);
foreach (MyClass myObj in myObjList)
{
bw.Write(JsonConvert.SerializeObject(myObj));
}
bw.Close();
fs.Close();
}
I am looking something like
FileStream fs = new FileStream(filePath, FileMode.Create);
BinaryReader bw = new BinaryReader(fs);
while (!filePath.EOF)
{
List<MyClass> myObjList = br.Read(myFile);
}
anyone can help with this?
thanks in advance

JSON can be saved with no formatting (no new lines), so you can save 1 record per row of a file. Thus, my suggested solution is to ignore binary files and instead use a regular StreamWriter:
private void WriteToFile(List<MyClass> myObjList, string filePath)
{
using (StreamWriter sw = File.CreateText(filePath))
{
foreach (MyClass myObj in myObjList)
{
sw.Write(JsonConvert.SerializeObject(myObj, Newtonsoft.Json.Formatting.None));
}
}
}
private List<MyClass> ReadFromFile(string filePath)
{
List<MyClass> myObjList = new List<MyClass>();
using (StreamReader sr = File.OpenText(filePath))
{
string line = null;
while ((line = sr.ReadLine()) != null)
{
myObjList.Add(JsonConvert.DeserializeObject<MyClass>(line));
}
}
return myObjList;
}
If you really want to use the binary writer to save JSON, you could change it to be like this:
private void WriteToBinFile(List<MyClass> myObjList, string filePath)
{
using (FileStream fs = new FileStream(filePath, FileMode.Create))
using (BinaryWriter bw = new BinaryWriter(fs))
{
foreach (MyClass myObj in myObjList)
{
bw.Write(JsonConvert.SerializeObject(myObj));
}
}
}
private List<MyClass> ReadFromBinFile(string filePath)
{
List<MyClass> myObjList = new List<MyClass>();
using (FileStream fs = new FileStream(filePath, FileAccess.Read))
using (BinaryReader br = new BinaryReader(fs))
{
while (fs.Length != fs.Position) // This will throw an exception for non-seekable streams (stream.CanSeek == false), but filestreams are seekable so it's OK here
{
myObjList.Add(JsonConvert.DeserializeObject<MyClass>(br.ReadString()));
}
}
return myObjList;
}
Notes:
I've added using around your stream instantiations so that the files are properly closed when memory is freed
To check the stream is at the end, you have to compare Length to Position.

The process cannot access the file because it is being used by another process

public bool ReadFile()
{
string fname = "text.txt";
FileStream fs = null;
fs = new FileStream(fname, FileMode.OpenOrCreate,FileAccess.Read);
StreamReader sr = new StreamReader(fs);
string res = sr.ReadToEnd();
if (res == "1")
return true;
else
return false;
}
public void WriteToFile()
{
string fname = "text.txt";
FileStream fs = null;
fs = new FileStream(fname, FileMode.Open,FileAccess.Write);
StreamWriter sw = new StreamWriter(fs);
sw.Write("1");
}
So it should work like if ReadFile returns false than i do WriteFile.
But when it reaches writefile, it throws IO expection:
The process cannot access the file ... because it is being used by another process

You aren't closing the file when you read it.
Put your FileStream and StreamReader objects in using statements:
using (var fs = new FileStream(fname, FileMode.OpenOrCreate,FileAccess.Read)) {
using (var sr = new StreamReader(fs)) {
//read file here
}
}
Make sure you do the same when you write to the file.

You need to dispose the StreamReader object in the ReadFile method. The StreamReader inherits from IDisposable and therfor you need to dispose the object.
Check this link for more info:StreamReader Class

file I/O in xna windows phone.... reading and writing text data

i wants to increment the score of player and check the highscore, so that i am storing score in text file.i am trying below code but it is throwing exception.
Exception : Value does not fall within the expected range.
public void storage()
{
var appstorage = IsolatedStorageFile.GetUserStoreForApplication();
String filename = "store.txt";
using (var file = appstorage.OpenFile(filename, FileMode.OpenOrCreate,FileAccess.ReadWrite))
{
using (var writer = new StreamWriter(file))
{
writer.Write(score);
}
using(var reader=new StreamReader(file))
{
playerscore =reader.ReadLine();
}
}
}

I am really not sure about windows phone support but in windows I would do it something like this
using (var file = File.Open(filename, FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
using (var writer = new BinaryWriter(file))
{
writer.Write(score);
}
using (var reader = new BinaryReader(file))
{
playerscore = reader.ReadInt32();
}
}
Of course if you can only read an write text this would be the solution
using (var file = File.Open(filename, FileMode.OpenOrCreate,` FileAccess.ReadWrite))
{
using (var writer = new StreamWriter(file))
{
writer.WriteLine(score.ToString());
}
using (var reader = new StreamReader(file))
{
playerscore = int.Parse(reader.ReadLine());
}
}

Create File If File Does Not Exist

I need to get my code to read if file doesnt exist create else append. Right now it is reading if it does exist create and append. Here is the code:
if (File.Exists(path))
{
using (StreamWriter sw = File.CreateText(path))
{
Would I do this?
if (! File.Exists(path))
{
using (StreamWriter sw = File.CreateText(path))
{
Edit:
string path = txtFilePath.Text;
if (!File.Exists(path))
{
using (StreamWriter sw = File.CreateText(path))
{
foreach (var line in employeeList.Items)
{
sw.WriteLine(((Employee)line).FirstName);
sw.WriteLine(((Employee)line).LastName);
sw.WriteLine(((Employee)line).JobTitle);
}
}
}
else
{
StreamWriter sw = File.AppendText(path);
foreach (var line in employeeList.Items)
{
sw.WriteLine(((Employee)line).FirstName);
sw.WriteLine(((Employee)line).LastName);
sw.WriteLine(((Employee)line).JobTitle);
}
sw.Close();
}
}

You can simply call
using (StreamWriter w = File.AppendText("log.txt"))
It will create the file if it doesn't exist and open the file for appending.
Edit:
This is sufficient:
string path = txtFilePath.Text;
using(StreamWriter sw = File.AppendText(path))
{
foreach (var line in employeeList.Items)
{
Employee e = (Employee)line; // unbox once
sw.WriteLine(e.FirstName);
sw.WriteLine(e.LastName);
sw.WriteLine(e.JobTitle);
}
}
But if you insist on checking first, you can do something like this, but I don't see the point.
string path = txtFilePath.Text;
using (StreamWriter sw = (File.Exists(path)) ? File.AppendText(path) : File.CreateText(path))
{
foreach (var line in employeeList.Items)
{
sw.WriteLine(((Employee)line).FirstName);
sw.WriteLine(((Employee)line).LastName);
sw.WriteLine(((Employee)line).JobTitle);
}
}
Also, one thing to point out with your code is that you're doing a lot of unnecessary unboxing. If you have to use a plain (non-generic) collection like ArrayList, then unbox the object once and use the reference.
However, I perfer to use List<> for my collections:
public class EmployeeList : List<Employee>

or:
using FileStream fileStream = File.Open(path, FileMode.Append);
using StreamWriter file = new StreamWriter(fileStream);
// ...

You don't even need to do the check manually, File.Open does it for you. Try:
using (StreamWriter sw = new StreamWriter(File.Open(path, System.IO.FileMode.Append)))
{
Ref: http://msdn.microsoft.com/en-us/library/system.io.filemode.aspx

2021
Just use File.AppendAllText, which creates the file if it does not exist:
File.AppendAllText("myFile.txt", "some text");

Yes, you need to negate File.Exists(path) if you want to check if the file doesn't exist.

This works as well for me
string path = TextFile + ".txt";
if (!File.Exists(HttpContext.Current.Server.MapPath(path)))
{
File.Create(HttpContext.Current.Server.MapPath(path)).Close();
}
using (StreamWriter w = File.AppendText(HttpContext.Current.Server.MapPath(path)))
{
w.WriteLine("{0}", "Hello World");
w.Flush();
w.Close();
}

This will enable appending to file using StreamWriter
using (StreamWriter stream = new StreamWriter("YourFilePath", true)) {...}
This is default mode, not append to file and create a new file.
using (StreamWriter stream = new StreamWriter("YourFilePath", false)){...}
or
using (StreamWriter stream = new StreamWriter("YourFilePath")){...}
Anyhow if you want to check if the file exists and then do other things,you can use
using (StreamWriter sw = (File.Exists(path)) ? File.AppendText(path) : File.CreateText(path))
{...}

For Example
string rootPath = Path.GetPathRoot(Environment.GetFolderPath(Environment.SpecialFolder.System));
rootPath += "MTN";
if (!(File.Exists(rootPath)))
{
File.CreateText(rootPath);
}

private List<Url> AddURLToFile(Urls urls, Url url)
{
string filePath = #"D:\test\file.json";
urls.UrlList.Add(url);
//if (!System.IO.File.Exists(filePath))
// using (System.IO.File.Delete(filePath));
System.IO.File.WriteAllText(filePath, JsonConvert.SerializeObject(urls.UrlList));
//using (StreamWriter sw = (System.IO.File.Exists(filePath)) ? System.IO.File.AppendText(filePath) : System.IO.File.CreateText(filePath))
//{
// sw.WriteLine(JsonConvert.SerializeObject(urls.UrlList));
//}
return urls.UrlList;
}
private List<Url> ReadURLToFile()
{
// string filePath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), #"App_Data\file.json");
string filePath = #"D:\test\file.json";
List<Url> result = new List<Url>(); ;
if (!System.IO.File.Exists(filePath))
using (System.IO.File.CreateText(filePath)) ;
using (StreamReader file = new StreamReader(filePath))
{
result = JsonConvert.DeserializeObject<List<Url>>(file.ReadToEnd());
file.Close();
}
if (result == null)
result = new List<Url>();
return result;
}

C# Comparing two files and exporting matching lines based on delimiter

Here’s the scenario.
I have a text file(alpha), single column, with a bunch of items.
My 2nd file is a csv(delta) with 4 columns.
I have to have the alpha compare again the delta and create a new file (omega) in which anything that alpha matched delta, it would export only the first two columns from delta into a new .txt file.
Example:
(Alpha)
BeginID
(delta):
BeginID,Muchmore,Info,Exists
(Omega):
BeginID,Muchmore
This document will probably have 10k lines it in. Thanks for the help!

Here's a rough cut way of doing the task you need:
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
string alphaFilePath = #"C:\Documents and Settings\Jason\My Documents\Visual Studio 2008\Projects\Compte Two Files\Compte Two Files\ExternalFiles\Alpha.txt";
List<string> alphaFileContent = new List<string>();
using (FileStream fs = new FileStream(alphaFilePath, FileMode.Open))
using(StreamReader rdr = new StreamReader(fs))
{
while(!rdr.EndOfStream)
{
alphaFileContent.Add(rdr.ReadLine());
}
}
string betaFilePath = #"C:\Beta.csv";
StringBuilder sb = new StringBuilder();
using (FileStream fs = new FileStream(betaFilePath, FileMode.Open))
using (StreamReader rdr = new StreamReader(fs))
{
while(! rdr.EndOfStream)
{
string[] betaFileLine = rdr.ReadLine().Split(Convert.ToChar(","));
if (alphaFileContent.Contains(betaFileLine[0]))
{
sb.AppendLine(String.Format("{0}, {1}", betaFileLine[0], betaFileLine[1]));
}
}
}
using (FileStream fs = new FileStream(#"C:\Omega.txt", FileMode.Create))
using (StreamWriter writer = new StreamWriter(fs))
{
writer.Write(sb.ToString());
}
Console.WriteLine(sb.ToString());
}
}
}
Basically it reads a txt file, puts the contents in a list. Then it reads a csv file (assuming no columns) and matches the values to create a StringBuilder. In your code, substitute the StringBuilder with creating a new txt file.
EDIT: If you wish to have the code run in a button click, then put it in the button click handler (or a new routine and call that):
public void ButtonClick (Object sender, EventArgs e)
{
string alphaFilePath = #"C:\Documents and Settings\Jason\My Documents\Visual Studio 2008\Projects\Compte Two Files\Compte Two Files\ExternalFiles\Alpha.txt";
List<string> alphaFileContent = new List<string>();
using (FileStream fs = new FileStream(alphaFilePath, FileMode.Open))
using(StreamReader rdr = new StreamReader(fs))
{
while(!rdr.EndOfStream)
{
alphaFileContent.Add(rdr.ReadLine());
}
}
string betaFilePath = #"C:\Beta.csv";
StringBuilder sb = new StringBuilder();
using (FileStream fs = new FileStream(betaFilePath, FileMode.Open))
using (StreamReader rdr = new StreamReader(fs))
{
while(! rdr.EndOfStream)
{
string[] betaFileLine = rdr.ReadLine().Split(Convert.ToChar(","));
if (alphaFileContent.Contains(betaFileLine[0]))
{
sb.AppendLine(String.Format("{0}, {1}", betaFileLine[0], betaFileLine[1]));
}
}
}
using (FileStream fs = new FileStream(#"C:\Omega.txt", FileMode.Create))
using (StreamWriter writer = new StreamWriter(fs))
{
writer.Write(sb.ToString());
}
}

I'd probably load alpha into a collection then open delta for read, while not EOF readline into a string, split, if collection.contains column 0 then write to omega.
Done...