Develop Reference

Trying to create a bin-file using stream

I onced managed to create the bin-file in my project. I changed the primary key from int to Guid and moved code from Main to my class Quote. At the moment I can only add new entries in said file. If I remove it a new file(0 bytes) is created and the stream gets ArgumentException when I try to feed the file dummy-data. I am trying to use an if-loop to handle stream.Lenght == 0.
public static List<Quote> readBinaryToList() //Crashes if binfile is 0 bytes long
{
IFormatter formatter = new BinaryFormatter();
Stream stream = new FileStream(#"C:\Users\xxxxxx\Desktop\quotes.bin", FileMode.OpenOrCreate, FileAccess.Read, FileShare.Read);
if (stream.Length == 0)
{
Quote q = new Quote(Guid.NewGuid(), "Quote dummy", false);
List<Quote> quoteList = new List<Quote>();
quoteList.Add(q);
var bformatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
bformatter.Serialize(stream, quoteList);
bformatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
List<Quote> quoteListTmp = (List<Quote>)bformatter.Deserialize(stream);
return quoteList;
}
else
{
List<Quote> quoteList = (List<Quote>)formatter.Deserialize(stream);
stream.Close();
return quoteList;
}
}

As pointed out in previous answers, you must give your file stream write permissions which can be done in its constructor, then you should also set the position of the stream back to 0, you can achieve this by using the stream's Position property.
You are creating a lot of unnecessary objects that don't actually contribute to purpose of the method I have omitted these below. In doing so, setting the streams Position property to 0 is redundant but I've left it in a comment to show how its done.
Some other things to consider: Declare the file stream inside a using statement so that it is disposed when the method comes to an end this means you can omit the manual close in the else statement. Some of your code can be written more tersely, this is just a personal preference but I think it would be best to inline some of your code to remove as much noise as possible. It is also convention in C# to use PascalCase for Methods.
public static List<Quote> ReadBinaryToList(){
using(Stream stream = new FileStream(#"quotes.bin", FileMode.OpenOrCreate, FileAccess.ReadWrite)) {
IFormatter formatter = new BinaryFormatter();
if (stream.Length == 0) {
List<Quote> quoteList = new List<Quote> {new Quote(Guid.NewGuid(), "Quote dummy", false)};
formatter.Serialize(stream, quoteList);
//stream.Position = 0;
return quoteList;
}
else return (List<Quote>)formatter.Deserialize(stream);
}
}

The file is being opened as readonly, serializing to the file will require write permissions.
Stream stream = new FileStream(#"C:\temp\quotes.bin", FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.Read);
The stream should also be returned to the beginning before making any attempts to deserialize from it.
stream.Seek(0, SeekOrigin.Begin);
FileStreams have a single "head" where all read and write operations take places. As a new stream is being written, the head is always at the end and any attempt to read from the end will fail. Some streams (e.g. NetworkStream) behave differently and do not allow seeking at all.
Also, the initial position of the FileStream depends on how the file is opened (based on the specified FileMode). The FileMode specified in the question will result in the stream position starting at the beginning of the file, so this is not required in the else block.
And make sure that the Quote class is marked [Serializable]

How can I convert StreamWriter to a Stream?

I am trying to create a file using FileHelpers and then write that file out using SshNet all in memory.
So far I have the following:
var engine = new FileHelperEngine<MyObject>();
MemoryStream ms = new MemoryStream();
StreamWriter sw = new StreamWriter(ms);
engine.WriteStream(sw, MyData);
SshHelper ssh = new SshHelper("","","");
ssh.WriteFile("MyPath", sw.BaseStream);
However my issue is with the WriteFile method since it requires a Stream parameter and when I run my code I am getting an empty file.
How can I convert my StreamWriter (sw variable) into a Stream parameter?
EDIT:
I've tried both(not at the same time):
ms.Seek(0, SeekOrigin.Begin);
ms.Position = 0;
and it still writes a 0 byte file.
I further tested by using FileHelper to write to my local disk to verify that I have data. (Which I do)

your MemoryStream is the stream, the StreamWriter is just writing to it. Try passing ms in, instead of sw.

Before WriteFile try setting the Position of your Stream to 0: ms.Seek( 0, SeekOrigin.Begin )

Convert string to filestream in c#

Just started with writing unit tests and I am now, blocked with this situation:
I have a method which has a FileStream object and I am trying to pass a "string" to it.
So, I would like to convert my string to FileStream and I am doing this:
File.WriteAllText(string.Concat(Environment.ExpandEnvironmentVariables("%temp%"),
#"/test.txt"), testFileContent); //writes my string to a temp file!
new FileStream(string.Concat(Environment.ExpandEnvironmentVariables("%temp%"),
#"/test.txt"), FileMode.Open) //open that temp file and uses it as a fileStream!
close the file then!
But, I guess there must be some very simple alternative to convert a string to a fileStream.
Suggestions are welcome! [Note there are other answers to this question in stackoverflow but none seems to be a straight forward solution to that]
Thanks in advance!

First of all change your method to allow Stream instead of FileStream. FileStream is an implementation which, as I remember, does not add any methods or properties, just implement abstract class Stream. And then using below code you can convert string to Stream:
public Stream GenerateStreamFromString(string s)
{
MemoryStream stream = new MemoryStream();
StreamWriter writer = new StreamWriter(stream);
writer.Write(s);
writer.Flush();
stream.Position = 0;
return stream;
}

As FileStream class provides a stream for a file and hence it's constructor requires the path of the file,mode, permission parameter etc. to read the file into stream and hence it is used to read the text from file into stream. If we need to convert string to stream first we need to convert string to bytes array as stream is a sequence of bytes. Below is the code.
//Stream is a base class it holds the reference of MemoryStream
Stream stream = new MemoryStream();
String strText = "This is a String that needs to beconvert in stream";
byte[] byteArray = Encoding.UTF8.GetBytes(strText);
stream.Write(byteArray, 0, byteArray.Length);
//set the position at the beginning.
stream.Position = 0;
using (StreamReader sr = new StreamReader(stream))
{
string strData;
while ((strData= sr.ReadLine()) != null)
{
Console.WriteLine(strData);
}
}

Write to a stream as if it were a file, but really write to an object

I am trying write a stream to the ram instead of a file. I tried doing this:
Stream stream = new MemoryStream();
BinaryFormatter bFormatter = new BinaryFormatter();
bFormatter.Serialize(stream, objectToSerialize);
stream.Close();
return stream;
But when I look at the stream after I have supposedly written to it it is saying "Length = 'stream.Length' threw an exception of type 'System.ObjectDisposedException'"

Don't close the stream before getting the data, and don't return the stream but the content of the stream:
using (Stream stream = new MemoryStream()) {
BinaryFormatter bFormatter = new BinaryFormatter();
bFormatter.Serialize(stream, objectToSerialize);
return stream.ToArray();
}

You're calling stream.Close(), which is exactly the same as calling Dispose() on the stream.
Just remove that line of code, and you should be fine. Basically, you need to leave the MemoryStream open when it's returned.
On a different note, depending on what you're going to do, you may also want to reset the stream's position. I suspect you'll want:
Stream stream = new MemoryStream();
BinaryFormatter bFormatter = new BinaryFormatter();
bFormatter.Serialize(stream, objectToSerialize);
stream.Position = 0;
return stream;
This works the same as your code, but does not Dispose() the stream (since it's no longer calling stream.Close()), and also resets it to the start position, which is often required if you want to read the object/data back out.

Don't call stream.Close (or IDisposable.Dispose()) until you're done with the stream.
You probably need to set the stream position back to start stream.Position = 0;
Make sure that you do dispose of the stream when you're done. The using statement is your friend here.

It's because you stream.Close(); the object.

You are getting the exception because you call Close(). From MSDN: Stream Class
Closes the current stream and releases any resources (such as sockets
and file handles) associated with the current stream.
You should be able to simply remove stream.Close();.

"Object can be disposed of more than once" error

When I run code analysis on the following chunk of code I get this message:
Object 'stream' can be disposed more than once in method 'upload.Page_Load(object, EventArgs)'. To avoid generating a System.ObjectDisposedException you should not call Dispose more than one time on an object.
using(var stream = File.Open(newFilename, FileMode.CreateNew))
using(var reader = new BinaryReader(file.InputStream))
using(var writer = new BinaryWriter(stream))
{
var chunk = new byte[ChunkSize];
Int32 count;
while((count = reader.Read(chunk, 0, ChunkSize)) > 0)
{
writer.Write(chunk, 0, count);
}
}
I don't understand why it might be called twice, and how to fix it to eliminate the error. Any help?

I struggled with this problem and found the example here to be very helpful. I'll post the code for a quick view:
using (Stream stream = new FileStream("file.txt", FileMode.OpenOrCreate))
{
using (StreamWriter writer = new StreamWriter(stream))
{
// Use the writer object...
}
}
Replace the outer using statement with a try/finally making sure to BOTH null the stream after using it in StreamWriter AND check to make sure it is not null in the finally before disposing.
Stream stream = null;
try
{
stream = new FileStream("file.txt", FileMode.OpenOrCreate);
using (StreamWriter writer = new StreamWriter(stream))
{
stream = null;
// Use the writer object...
}
}
finally
{
if(stream != null)
stream.Dispose();
}
Doing this cleared up my errors.

To illustrate, let's edit your code
using(var stream = File.Open(newFilename, FileMode.CreateNew))
{
using(var reader = new BinaryReader(file.InputStream))
{
using(var writer = new BinaryWriter(stream))
{
var chunk = new byte[ChunkSize];
Int32 count;
while((count = reader.Read(chunk, 0, ChunkSize)) > 0)
{
writer.Write(chunk, 0, count);
}
} // here we dispose of writer, which disposes of stream
} // here we dispose of reader
} // here we dispose a stream, which was already disposed of by writer
To avoid this, just create the writer directly
using(var reader = new BinaryReader(file.InputStream))
{
using(var writer = new BinaryWriter( File.Open(newFilename, FileMode.CreateNew)))
{
var chunk = new byte[ChunkSize];
Int32 count;
while((count = reader.Read(chunk, 0, ChunkSize)) > 0)
{
writer.Write(chunk, 0, count);
}
} // here we dispose of writer, which disposes of its inner stream
} // here we dispose of reader
edit: to take into account what Eric Lippert is saying, there could indeed be a moment when the stream is only released by the finalizer if BinaryWriter throws an exception. According to the BinaryWriter code, that could occur in three cases
If (output Is Nothing) Then
Throw New ArgumentNullException("output")
End If
If (encoding Is Nothing) Then
Throw New ArgumentNullException("encoding")
End If
If Not output.CanWrite Then
Throw New ArgumentException(Environment.GetResourceString("Argument_StreamNotWritable"))
End If
if you didn't specify an output, ie if stream is null. That shouldn't be a problem since a null stream means no resources to dispose of :)
if you didn't specify an encoding. since we don't use the constructor form where the encoding is specified, there should be no problem here either (i didn't look into the encoding contructor too much, but an invalid codepage can throw)
if you don't pass a writable stream. That should be caught quite quickly during development...
Anyway, good point, hence the edit :)

The BinaryReader/BinaryWriter will dispose the underlying stream for you when it disposes. You don't need to do it explicitly.
To fix it you can remove the using around the Stream itself.

A proper implementation of Dispose is explicitly required not to care if it's been called more than once on the same object. While multiple calls to Dispose are sometimes indicative of logic problems or code which could be better written, the only way I would improve the original posted code would be to convince Microsoft to add an option to BinaryReader and BinaryWriter instructing them not to dispose their passed-in stream (and then use that option). Otherwise, the code required to ensure the file gets closed even if the reader or writer throws in its constructor would be sufficiently ugly that simply letting the file get disposed more than once would seem cleaner.

Your writer will dispose your stream, always.

Suppress CA2202 whenever you are sure that the object in question handles multiple Dispose calls correctly and that your control flow is impeccably readable. BCL objects generally implement Dispose correctly. Streams are famous for that.
But don't necessarily trust third party or your own streams if you don't have unit tests probing that scenario yet. An API which returns a Stream may be returning a fragile subclass.