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;
}
Related
I was trying to read CSV file in C#.
I have tried File.ReadAllLines(path).Select(a => a.Split(';')) way but the issue is when there is \n multiple line in a cell it is not working.
So I have tried below
using LumenWorks.Framework.IO.Csv;
var csvTable = new DataTable();
using (TextReader fileReader = File.OpenText(path))
using (var csvReader = new CsvReader(fileReader, false))
{
csvTable.Load(csvReader);
}
for (int i = 0; i < csvTable.Rows.Count; i++)
{
if (!(csvTable.Rows[i][0] is DBNull))
{
var row1= csvTable.Rows[i][0];
}
if (!(csvTable.Rows[i][1] is DBNull))
{
var row2= csvTable.Rows[i][1];
}
}
The issue is the above code throwing exception as
The CSV appears to be corrupt near record '0' field '5 at position '63'
This is because the header of CSV's having two double quote as below
"Header1",""Header2""
Is there a way that I can ignore double quotes and process the CSV's.
update
I have tried with TextFieldParser as below
public static void GetCSVData()
{
using (var parser = new TextFieldParser(path))
{
parser.HasFieldsEnclosedInQuotes = false;
parser.Delimiters = new[] { "," };
while (parser.PeekChars(1) != null)
{
string[] fields = parser.ReadFields();
foreach (var field in fields)
{
Console.Write(field + " ");
}
Console.WriteLine(Environment.NewLine);
}
}
}
The output:
Sample CSV data I have used:
Any help is appreciated.
Hope this works!
Please replace two double quotes as below from csv:
using (FileStream fs = new FileStream(Path, FileMode.Open, FileAccess.ReadWrite, FileShare.None))
{
StreamReader sr = new StreamReader(fs);
string contents = sr.ReadToEnd();
// replace "" with "
contents = contents.Replace("\"\"", "\"");
// go back to the beginning of the stream
fs.Seek(0, SeekOrigin.Begin);
// adjust the length to make sure all original
// contents is overritten
fs.SetLength(contents.Length);
StreamWriter sw = new StreamWriter(fs);
sw.Write(contents);
sw.Close();
}
Then use the same CSV helper
using LumenWorks.Framework.IO.Csv;
var csvTable = new DataTable();
using (TextReader fileReader = File.OpenText(path))
using (var csvReader = new CsvReader(fileReader, false))
{
csvTable.Load(csvReader);
}
Thanks.
I am doing a project Windows form for assignment in Uni, I want to search an already created text file to match a first name and last name then write some additional information if the name and last name exist. I have the code constructed and showing no errors, however when I run and attempt to add information I am being provided with an error which essentially says the next process (Streamreader writer can not access the file as it is already in use by another process) I assume this process is streamreader, I have tried to code it to stop reading to no avail. I am in my first 3 months learning coding and would appreciate some assistance if possible, I have put a snippet of my code below.
//check if there is a file with that name
if (File.Exists(sFile))
{
using (StreamReader sr = new StreamReader(sFile))
{
//while there is more data to read
while (sr.Peek() != -1)
{
//read first name and last name
sFirstName = sr.ReadLine();
sLastName = sr.ReadLine();
}
{
//does this name match?
if (sFirstName + sLastName == txtSearchName.Text)
sr.Close();
}
//Process write to file
using (StreamWriter sw = new StreamWriter(sFile, true))
{
sw.WriteLine("First Name:" + sFirstName);
sw.WriteLine("Last Name:" + sLastName);
sw.WriteLine("Gender:" + sGender);
}
You are using your writer inside the reader, using the same file.
A using disposes the object inside it, after the closing curly braces.
using(StreamReader reader = new StreamReader("foo")){
//... some stuff
using(Streamwriter writer = new StreamWriter("foo")){
}
}
Do it like so :
using(StreamReader reader = new StreamReader("foo")){
//... some stuff
}
using(Streamwriter writer = new StreamWriter("foo")){
}
As per my comment regarding the using statement.
Rearrange to the below. I've tested locally and it seems to work.
using (StreamReader sr = new StreamReader(sfile))
{
//while there is more data to read
while (sr.Peek() != -1)
{
//read first name and last name
sFirstName = sr.ReadLine();
sLastName = sr.ReadLine();
//does this name match?
if (sFirstName + sLastName == txtSearchName.Text)
break;
}
}
using (StreamWriter sw = new StreamWriter(sfile, true))
{
sw.WriteLine("First Name:" + sFirstName);
sw.WriteLine("Last Name:" + sLastName);
sw.WriteLine("Gender:" + sGender);
}
I've replaced the sr.Close with a break statement to exit out. Closing the reader causes the subsequent peek to error as it's closed.
Also, I've noticed that you are not setting gender? unless its set elsewhere.
hope that helps
You can use FileStream. It gives you many options to work with file:
var fileStream = new FileStream("FileName", FileMode.Open,
FileAccess.Write, FileShare.ReadWrite);
var fileStream = new FileStream("fileName", FileMode.Open,
FileAccess.ReadWrite, FileShare.ReadWrite);
I think this is what you want/need. You can't append to a file the way you are trying to do it. Instead you'll want to read your input file, and write a temp file as you are reading through. And, whenever your line matches your requirements, then you can write the line with your modifications.
string inputFile = "C:\\temp\\StreamWriterSample.txt";
string tempFile = "C:\\temp\\StreamWriterSampleTemp.txt";
using (StreamWriter sw = new StreamWriter(tempFile))//get a writer ready
{
using (StreamReader sr = new StreamReader(inputFile))//get a reader ready
{
string currentLine = string.Empty;
while ((currentLine = sr.ReadLine()) != null)
{
if (currentLine.Contains("Clients"))
{
sw.WriteLine(currentLine + " modified");
}
else
{
sw.WriteLine(currentLine);
}
}
}
}
//now lets crush the old file with the new file
File.Copy(tempFile, inputFile, true);
i have trouble with the following two functions. Both have a indentical basic scheme but first one work, second one causes an exception at marked line("File is used by another process").
// this works
public static void EncryptFile(string FileName)
{
string ToEncrypt = null;
using(StreamReader sr = new StreamReader(FileName))
{
ToEncrypt = sr.ReadToEnd();
}
using(StreamWriter sw = new StreamWriter(FileName, false))
{
string Encrypted = Encrypt(ToEncrypt, true);
sw.Write(Encrypted);
}
}
// this works not - see commented lin
public static void DecryptFile(string FileName)
{
string ToDecrypt = null;
using (StreamReader sr = new StreamReader(FileName))
{
ToDecrypt = sr.ReadToEnd();
}
// here comes the exception
using (StreamWriter sw = new StreamWriter(FileName, false))
{
string Decrypted = Decrypt(ToDecrypt, true);
sw.Write(Decrypted);
}
}
I have tried with an additional Close() after read and write, but this works not too.
I hope, somebody can help.
Thanks
Torsten
Is the function called from multiple threads? If yes you may want to declare a static object on class level and place a lock statement around the entire body of that method. Like this:
private static Object syncObject = new Object()
// this works not - see commented lin
public static void DecryptFile(string FileName)
{
lock(syncObject)
{
string ToDecrypt = null;
using (StreamReader sr = new StreamReader(FileName))
{
ToDecrypt = sr.ReadToEnd();
}
// here comes the exception
using (StreamWriter sw = new StreamWriter(FileName, false))
{
string Decrypted = Decrypt(ToDecrypt, true);
sw.Write(Decrypted);
}
}
}
Also could you, just for fun, comment the StreamReader statement and try to run the method again? If it still doesn't work, check if you've that file open in a texteditor or something alike by using ProcessExplorer or something similiar.
edit
could you comment the StreamReader part? So that it looks like this:
public static void DecryptFile(string FileName)
{
//string ToDecrypt = null;
//using (StreamReader sr = new StreamReader(FileName))
//{
// ToDecrypt = sr.ReadToEnd();
//}
// here comes the exception
using (StreamWriter sw = new StreamWriter(FileName, false))
{
string Decrypted = Decrypt(ToDecrypt, true);
sw.Write(Decrypted);
}
}
also could you try to open an exclusive FileStream on that file before the StreamReader and once after the StreamReader but before the StreamWriter? http://msdn.microsoft.com/de-de/library/tyhc0kft%28v=vs.110%29.aspx
Also could you try and use another file for that method?
I was trying to create a fixed lenght(left aligned) batch file with the below code.
when i use Append it's throwing exception "is a method but used like a type".
string batFilePath = #"c:\mockforbat.bat";
if (!File.Exists(batFilePath))
{
using (FileStream fs = File.Create(batFilePath))
{
fs.Close();
}
}
//write
using (StreamWriter sw = new File.AppendText(batFilePath))
{
string a = String.Format("{0,-24}{1,-5}{2,5}", "CostCenter", "CostObject", "ActivityType");
sw.WriteLine(#a);
}
Process process = Process.Start(batFilePath);
process.WaitForExit();
Please some one correct me what i did wrong here ?
Drop the new operator from this line
using (StreamWriter sw = new File.AppendText(batFilePath))
It should read
using (StreamWriter sw = File.AppendText(batFilePath))
string batFilePath = #"c:\mockforbat.bat";
using(var fs = new FileStream(batFilePath , FileMode.OpenOrCreate, FileAccess.Write))
{
using(var sw = new StreamWriter(fs))
{
string a = String.Format("{0,-24}{1,-5}{2,5}", "CostCenter", "CostObject", "ActivityType");
sw.WriteLine(a);
}
}
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...