I can't figure out how to use FileStream to write data to a text file...
Assuming you have the data already:
string path = #"C:\temp\file"; // path to file
using (FileStream fs = File.Create(path))
{
// writing data in string
string dataasstring = "data"; //your data
byte[] info = new UTF8Encoding(true).GetBytes(dataasstring);
fs.Write(info, 0, info.Length);
// writing data in bytes already
byte[] data = new byte[] { 0x0 };
fs.Write(data, 0, data.Length);
}
(taken from msdn docs and modified)
The documentation for FileStream gives an excellent example.
In short you create a filestream object, and use the Encoding.UTF8 object (or the encoding you want to use) to convert your plaintext to bytes, in which you can use your filestream.write method.
But it would be easier to just use the File class, and File.Append* methods.
EDIT: Example
File.AppendAllText("/path/to/file", "content here");
From MSDN:
FileStream fs=new FileStream("c:\\Variables.txt", FileMode.Append, FileAccess.Write, FileShare.Write);
fs.Close();
StreamWriter sw=new StreamWriter("c:\\Variables.txt", true, Encoding.ASCII);
string NextLine="This is the appended line.";
sw.Write(NextLine);
sw.Close();
http://msdn.microsoft.com/en-us/library/system.io.filestream.aspx
Assuming your data is string based, this works well, changed your exception handling as you see fit. Making sure add a using System.IO for TextWriter and StreamWriter references.
using System.IO;
/// <summary>
/// Writes a message to the specified file name.
/// </summary>
/// <param name="Message">The message to write.</param>
/// <param name="FileName">The file name to write the message to.</param>
public void LogMessage(string Message, string FileName)
{
try
{
using (TextWriter tw = new StreamWriter(FileName, true))
{
tw.WriteLine(DateTime.Now.ToString() + " - " + Message);
}
}
catch (Exception ex) //Writing to log has failed, send message to trace in case anyone is listening.
{
System.Diagnostics.Trace.Write(ex.ToString());
}
}
using (var fs = new FileStream(textFilePath, FileMode.Append))
using (var sw = new StreamWriter(fs))
{
sw.WriteLine("This is the appended line.");
}
Related
I'm trying to read and write to the same file in a way such that no other program can access the file in between:
FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
StreamReader sr = new StreamReader(fs);
StreamWriter sw = new StreamWriter(fs);
newString = sr.ReadToEnd() + "somethingNew";
sw.Write(newString);
fs.Close();
The file is never written to. If I debug I can see that the reader manages to fetch the contents of the file, but the writer does not seem to be able to write to the file. Nothing happens.
I've been looking at this question which seems to be the same as mine. However I'm not able to get it to work.
Just Flush your changes to file, Have sw.Flush(); before closing the stream. like:
string filePath = "test.txt";
FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
StreamReader sr = new StreamReader(fs);
StreamWriter sw = new StreamWriter(fs);
newString = sr.ReadToEnd() + "somethingNew";
sw.Write(newString);
sw.Flush(); //HERE
fs.Close();
You may see this post simultaneous read-write a file in C# (open multiple streams for reading and writing)
As mentioned above - just add the Flush() to force the data held in the stream to be written to the file. In a comment you mentioned that you had previously used a 'using' statement but this hadn't worked.
Briefly here's why:
A using statement automatically calls Flush() so you don't have
to.
When you dispose of a StreamReader (or StreamWriter) - like by using a 'using' statement - the inner stream object is also disposed and you lose the handle to the stream.
#EJS a simple static method that you can use to create a new file if it does not exist as well as write to the same file if it does exist
Simple usage
string path = #"C:\SomePath\Name.txt";
if (!System.IO.File.Exists(path))
{
WriteAndOrAppendText(path, "File Created");
}
else if (System.IO.File.Exists(path))
{
WriteAndOrAppendText(path, "New Boot.");
}
private static void WriteAndOrAppendText(string path, string strText)
{
if (!File.Exists(path))
{
using (StreamWriter fileStream = new StreamWriter(path, true))
{
fileStream.WriteLine(strText);
fileStream.Flush();
fileStream.Close();
}
}
else
{
using (StreamWriter fileStream2 = new StreamWriter(path, true))
{
fileStream2.WriteLine(strText);
fileStream2.Flush();
fileStream2.Close();
}
}
}
For being able to create a file, append to it, and read the data in it while still allowing an application to write to it, as I believe you are trying to do, here's a set up I created:
string path = #"C:\SomePath\MyLogFile.txt";
public static string Log(string Message)
{
try
{
if (File.Exists(path) == false)
File.Create(path).Close(); // need this .Close()!!!
logCounter++;
string logString = logCounter + " " + DateTime.Now.ToShortDateString() + " " + DateTime.Now.ToShortTimeString() + ": " + Message + Environment.NewLine;
using (FileStream fs = new FileStream(path, FileMode.Append, FileAccess.Write, FileShare.ReadWrite))
{
using (StreamWriter sw = new StreamWriter(fs))
{
sw.Write(logString);
}
}
return logString; // only necessary so we can return an error in the Exception block
}
catch (Exception ex)
{
return "Logger: Cannot log data. " + ex.ToString();
}
}
It's actually required to use FileAccess.Write if you do FileMode.Append - instead of being able to use FileAccess.ReadWrite - but I found that didn't matter because whatever had been written would have been closed and flushed to the file, and I could still open the file and read it (it wouldn't be locked & blank) using these. I have sw.Write() because I have Environment.NewLine that I added into my logString, but I could've done sw.WriteLine() and removed that, if I had wanted to.
One caveat: File.Exists() has issues if the path is long - can't remember the limit, but just know that there is one, so don't put your file you're writing to several layers deep. Less is always better.
I'm making an encryption program and need to save the encrypted password to a file using the binary reader and writer. When i try and read the data out all I get is a number. What did I do wrong?
public static string readData(string fileName)
{
string data;
FileStream fStream = new FileStream(fileName, FileMode.Open, FileAccess.Read);
using (BinaryReader reader = new BinaryReader(fStream))
{
data = reader.Read().ToString();
}
return data;
}
And the writer
public static void writeData(string fileName, string data)
{
using (BinaryWriter writer = new BinaryWriter(File.Open (fileName, FileMode.Create)))
{
writer.Write(data);
}
}
Use reader.ReadString() instead.
data = reader.ReadString();
The Read method reads the next character and returns the corresponding integer value of it as you can see in the documentation.basically, you have written a string to your file in binary format, so you need to read it back.
That is because you are calling the Read method that returns a single integer.ยจ
You want to do ReadString.
using System.IO;
class test
{
public static void Main()
{
string path=#"c:\mytext.txt";
if(File.Exists(path))
{
File.Delete(path);
}
FileStream fs=new FileStream(path,FileMode.OpenOrCreate);
StreamWriter str=new StreamWriter(fs);
str.BaseStream.Seek(0,SeekOrigin.End);
str.Write("mytext.txt.........................");
str.WriteLine(DateTime.Now.ToLongTimeString()+" "+DateTime.Now.ToLongDateString());
string addtext="this line is added"+Environment.NewLine;
File.AppendAllText(path,addtext); //Exception occurrs ??????????
string readtext=File.ReadAllText(path);
Console.WriteLine(readtext);
str.Flush();
str.Close();
Console.ReadKey();
//System.IO.IOException: The process cannot access the file 'c:\mytext.txt' because it is //being used by another process.
// at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
}
}
Try This
string path = #"c:\mytext.txt";
if (File.Exists(path))
{
File.Delete(path);
}
{ // Consider File Operation 1
FileStream fs = new FileStream(path, FileMode.OpenOrCreate);
StreamWriter str = new StreamWriter(fs);
str.BaseStream.Seek(0, SeekOrigin.End);
str.Write("mytext.txt.........................");
str.WriteLine(DateTime.Now.ToLongTimeString() + " " +
DateTime.Now.ToLongDateString());
string addtext = "this line is added" + Environment.NewLine;
str.Flush();
str.Close();
fs.Close();
// Close the Stream then Individually you can access the file.
}
File.AppendAllText(path, addtext); // File Operation 2
string readtext = File.ReadAllText(path); // File Operation 3
Console.WriteLine(readtext);
In every File Operation, The File will be Opened and must be Closed prior Opened. Like wise in the Operation 1 you must Close the File Stream for the Further Operations.
You are writing to the file prior to closing your filestream:
using(FileStream fs=new FileStream(path,FileMode.OpenOrCreate))
using (StreamWriter str=new StreamWriter(fs))
{
str.BaseStream.Seek(0,SeekOrigin.End);
str.Write("mytext.txt.........................");
str.WriteLine(DateTime.Now.ToLongTimeString()+" "+DateTime.Now.ToLongDateString());
string addtext="this line is added"+Environment.NewLine;
str.Flush();
}
File.AppendAllText(path,addtext); //Exception occurrs ??????????
string readtext=File.ReadAllText(path);
Console.WriteLine(readtext);
The above code should work, using the methods you are currently using. You should also look into the using statement and wrap your streams in a using block.
File.AppendAllText does not know about the stream you have opened, so will internally try to open the file again. Because your stream is blocking access to the file, File.AppendAllText will fail, throwing the exception you see.
I suggest you used str.Write or str.WriteLine instead, as you already do elsewhere in your code.
Your file is created but contains nothing because the exception is thrown before str.Flush() and str.Close() are called.
using (var fs = new FileStream(filePath, FileMode.Append, FileAccess.Write, FileShare.ReadWrite))
using (var sw = new StreamWriter(fs))
{
sw.WriteLine(message);
}
Using aspose, I have converted the first page of a pdf document to a jpeg (to be used as a thumbnail in a 'Documents' section to one of my asp.net pages). This is, upto this point, stored in a FileStream - but I need a byte array to assign to the datavalue of an Image control. Can anyone point me in the right direction to converting this? I've had a good look around and I can't find the solution.
Thanks a lot.
This should work:
byte[] data = File.ReadAllBytes("path/to/file.jpg")
var memStream = new MemoryStream();
yourFileStream.CopyTo(memStream);
var bytes = memStream.ToArray();
you can try this....
/// <summary>
/// Function to get byte array from a file
/// </summary>
/// <param name="_FileName">File name to get byte array</param>
/// <returns>Byte Array</returns>
public byte[] FileToByteArray(string _FileName)
{
byte[] _Buffer = null;
try
{
// Open file for reading
System.IO.FileStream _FileStream = new System.IO.FileStream(_FileName, System.IO.FileMode.Open, System.IO.FileAccess.Read);
// attach filestream to binary reader
System.IO.BinaryReader _BinaryReader = new System.IO.BinaryReader(_FileStream);
// get total byte length of the file
long _TotalBytes = new System.IO.FileInfo(_FileName).Length;
// read entire file into buffer
_Buffer = _BinaryReader.ReadBytes((Int32)_TotalBytes);
// close file reader
_FileStream.Close();
_FileStream.Dispose();
_BinaryReader.Close();
}
catch (Exception _Exception)
{
// Error
Console.WriteLine("Exception caught in process: {0}", _Exception.ToString());
}
return _Buffer;
}
I've noticed that if I persist an object back into file using a Datacontractserializer, if the length of the new xml is shorter than the xml originally present in the file the remnants of the original xml outwith the length of the new xml will remain in the file and will break the xml.
Does anyone have a good solution to fix this?
Here's the code I am using to persist the object:
/// <summary>
/// Flushes the current instance of the given type to the datastore.
/// </summary>
private void Flush()
{
try
{
string directory = Path.GetDirectoryName(this.fileName);
if (!Directory.Exists(directory))
{
Directory.CreateDirectory(directory);
}
FileStream stream = null;
try
{
stream = new FileStream(this.fileName, FileMode.OpenOrCreate);
for (int i = 0; i < 3; i++)
{
try
{
using (XmlDictionaryWriter writer = XmlDictionaryWriter.CreateTextWriter(stream, new System.Text.UTF8Encoding(false)))
{
stream = null;
// The serializer is initialized upstream.
this.serializer.WriteObject(writer, this.objectValue);
}
break;
}
catch (IOException)
{
Thread.Sleep(200);
}
}
}
finally
{
if (stream != null)
{
stream.Dispose();
}
}
}
catch
{
// TODO: Localize this
throw;
//throw new IOException(String.Format(CultureInfo.CurrentCulture, "Unable to save persistable object to file {0}", this.fileName));
}
}
It's because of how you are opening your stream with:
stream = new FileStream(this.fileName, FileMode.OpenOrCreate);
Try using:
stream = new FileStream(this.fileName, FileMode.Create);
See FileMode documentation.
I believe this is due to using FileMode.OpenOrCreate. If the file already exits, I think the file is being opened and parts of the data are being overwritten from the start byte. If you change to using FileMode.Create it forces any existing files to be overwritten.