Does StreamWriter or StreamReader auto creates the file when is using like below?
StreamWriter write = new StreamWriter("foo");
Yes, it creates the file if it doesn't exist, as per the documentation for this constructor:
The path parameter can be a file name, including a file on a Universal
Naming Convention (UNC) share. If the file exists, it is overwritten;
otherwise, a new file is created.
Certain forms of the constructor can overwrite, append, or create a new file yes. Read http://msdn.microsoft.com/en-us/library/system.io.streamwriter.aspx for more details.
Related
How do I create a text file using ASP.Net? I tried using Streamwriter but it only writes to exist file:
using (StreamWriter _testData = new StreamWriter(Server.MapPath("~/data.txt"), false))
{
_testData.WriteLine(txtText.Text); // Write the file.
_testData.WriteLine(txtLink.Text); // Write the file.
}
So how do I create it. I have tried:
FileSystemObject.CreateTextFile(filename[,overwrite[,unicode]]);
but it did not work.
string FilePath = Server.MapPath("FILENAME.txt");
string FileContent = "Put File Content Here";
File.WriteAllText(FilePath, FileContent);
The constructor creates the file for you if it doesn't exist, so you shouldn't have to change anything. Just be aware that specifying "false" in the constructor will overwrite the file each time this code is executed.
Initializes a new instance of the StreamWriter class for the specified file by using the default encoding and buffer size. If the file exists, it can be either overwritten or appended to. If the file does not exist, this constructor creates a new file.
https://msdn.microsoft.com/en-us/library/36b035cb(v=vs.110).aspx
I am doing editor in c#, windows forms. I wish to save 'new content' of file in the same file (usual usage of 'save' option) but I receive IOException, [ the process cannot access the file ' filename' because it is being used by another process.
I have method that writes to a NEW file and it works. How to use it to overwrite current file.
Edit:
I am using binarywriter http://msdn.microsoft.com/en-us/library/atxb4f07.aspx
Chances are that when you loaded the file, you didn't close the FileStream or whatever you used to read it. Always use a using statement for your streams (and other types implementing IDisposable), and it shouldn't be a problem. (Of course if you actually have that file open in a separate application, that's a different problem entirely.)
So instead of:
// Bad code
StreamReader reader = File.OpenText("foo.txt");
string data = reader.ReadToEnd();
// Nothing is closing the reader here! It'll keep an open
// file handle until it happens to be finalized
You should use something more like:
string data;
using (TextReader reader = File.OpenText("foo.txt"))
{
data = reader.ReadToEnd();
}
// Use data here - the handle will have been closed for you
Or ideally, use the methods in File which do it all for you:
string text = File.ReadAllText("foo.txt");
Check if you're closing stream to the file. If not then you're blocking yourself.
Assuming that you have correctly closed the stream you used to open and read the file initially, to create, append or fail depending of file existence you should use the FileMode parameter in FileStream constructor.
Everything depends on the way you open the FileStream, see here: FileStream Constructor (String, FileMode)
if you specify FileMode Create:
Specifies that the operating system should create a new file. If the
file already exists, it will be overwritten. This requires
FileIOPermissionAccess.Write. System.IO.FileMode.Create is equivalent
to requesting that if the file does not exist, use CreateNew;
otherwise, use Truncate. If the file already exists but is a hidden
file, an UnauthorizedAccessException is thrown.
I am experiencing the following problem. I am using .NET Framework 1.1 and I am trying to overwrite a file using this code:
try
{
using (StringWriter writer = new StringWriter())
{
Server.Execute(path, writer);
using (StreamWriter sr = File.CreateText(filepath + fileName))
{
sr.WriteLine(writer.ToString());
}
}
}
catch (Exception exc)
{
...
}
Sometimes it works fine, but sometimes it does not overwrite the file and no exception is thrown. Could someone tell me what the issue may be or how to handle why it doesn't overwrite the file?
Why not just:
File.WriteAllText(Path.Combine(filepath, fileName), writer.ToString())
From MSDN:
Creates a new file, writes the specified string to the file, and then closes the file. If the target file already exists, it is overwritten.
Could someone tell me what the issue may be or how to handle why it
doesn't overwrite the file?
Well, to answer your actual question, File.CreateText(string file) is behaving exactly as intended. if filepath + fileName to use your example, is a file that already exists, it opens the file instead of creating it. (It does not overwrite).
You could first check to see if the file exists using File.Exists(string file) then File.Delete(string file).
If File.CreateText(string file) doesn't suit your needs, you could try a different type. Maybe FileInfo?
Microsoft Says:
Creates or opens a file for writing UTF-8 encoded text.
Source: https://msdn.microsoft.com/en-us/library/system.io.file.createtext%28v=vs.110%29.aspx
over write can also be achieved with built in file.copy method.
File.copy has overload -
File.Copy Method (Source, Destination, OverWrite)
more info on msdn
hope this helps.
i am trying to use GZipStream to create a gz file using c#.
my problem is that i have a list that contains strings. and i need to create a password protected zip file, and put in it a text file containing the strings.
i don't want to create the textfile, then zip it, and then delete the textfile. i want to directly create a password protected zip file that contains the text file.
any help?
EDIT: i am done with the zipping stuff. now i need to set a pass for the created zip file. any help?
You should consider using SharpZipLib. It's an open source .net compression library. It includes examples on how to create either a .gz or a .zip file. Note that you can write directly to the .zip file. You don't need to create an intermediate file on disk first.
Edit: (in response to your edit) SharpZipLib supports zip passwords too.
Just create a StreamWriter wrapping your GZipStream, and write text to it.
GZipStream can be used to create a .gz file, but this is not the same as a .zip file.
For creating password-protected zip files, I think you need to go to a third-party library.
Here's how to do it using DotNetZip...
var sb = new System.Text.StringBuilder();
sb.Append("This is the text file...");
foreach (var item in listOfStrings)
sb.Append(item);
// sb now contains all the content that will be placed into
// the text file entry inside the zip.
using (var zip = new Ionic.Zip.ZipFile())
{
// set the password on the zip (implicitly enables encryption)
zip.Password = "Whatever.You.Like!!";
// optional: select strong encryption
zip.Encryption = Ionic.Zip.EncryptionAlgorithm.WinZipAes256;
// add an entry to the zip, specify a name, specify string content
zip.AddEntry("NameOfFile.txt", sb.ToString());
// save the file
zip.Save("MyFile.zip");
}
I have a string with a C# program that I want to write to a file and always overwrite the existing content. If the file isn't there, the program should create a new file instead of throwing an exception.
System.IO.File.WriteAllText (#"D:\path.txt", contents);
If the file exists, this overwrites it.
If the file does not exist, this creates it.
Please make sure you have appropriate privileges to write at the location, otherwise you will get an exception.
Use the File.WriteAllText method. It creates the file if it doesn't exist and overwrites it if it exists.
Generally, FileMode.Create is what you're looking for.
Use the file mode enum to change the File.Open behavior. This works for binary content as well as text.
Since FileMode.Open and FileMode.OpenOrCreate load the existing content to the file stream, if you want to replace the file completely you need to first clear the existing content, if any, before writing to the stream. FileMode.Truncate performs this step automatically
// OriginalFile:
oooooooooooooooooooooooooooooo
// NewFile:
----------------
// Write to file stream with FileMode.Open:
----------------oooooooooooooo
var exists = File.Exists(path);
var fileMode = exists
? FileMode.Truncate // overwrites all of the content of an existing file
: FileMode.CreateNew // creates a new file
using (var destinationStream = File.Open(path, fileMode)
{
await newContentStream.CopyToAsync(destinationStream);
}
FileMode Enum
If your code doesn't require the file to be truncated first, you can use the FileMode.OpenOrCreate to open the filestream, which will create the file if it doesn't exist or open it if it does. You can use the stream to point at the front and start overwriting the existing file?
I'm assuming your using a streams here, there are other ways to write a file.