How to write contents of one file to another file?

Question

I need to write contents of a file to another file using File.OpenRead and File.OpenWrite methods. I am unable to figure out how to do it.

How can i modify the following code to work for me.

using (FileStream stream = File.OpenRead("C:\\file1.txt"))
using (FileStream writeStream = File.OpenWrite("D:\\file2.txt"))
{
       BinaryReader reader = new BinaryReader(stream);
       BinaryWriter writer = new BinaryWriter(writeStream);
       writer.Write(reader.ReadBytes(stream.Length));
}

Answer 1

    using (FileStream stream = File.OpenRead("C:\\file1.txt"))
    using (FileStream writeStream = File.OpenWrite("D:\\file2.txt"))
    {
        BinaryReader reader = new BinaryReader(stream);
        BinaryWriter writer = new BinaryWriter(writeStream);

        // create a buffer to hold the bytes 
        byte[] buffer = new Byte[1024];
        int bytesRead;

        // while the read method returns bytes
        // keep writing them to the output stream
        while ((bytesRead =
                stream.Read(buffer, 0, 1024)) > 0)
        {
            writeStream.Write(buffer, 0, bytesRead);
        }
    }

Just wonder why not to use this:

File.Copy("C:\\file1.txt", "D:\\file2.txt");

Answer 2

You should be using File.Copy unless you want to append to the second file.

If you want to append you can still use the File class.

string content = File.ReadAllText("C:\\file1.txt");
File.AppendAllText("D:\\file2.txt",content);

This works for file with small size as entire file in loaded into the memory.

Answer 3

Try something along these lines:

using (FileStream input = File.OpenRead(pathToInputFile),
    output = File.OpenWrite(pathToOutputFile))
{
    int read = -1;
    byte[] buffer = new byte[4096];
    while (read != 0)
    {
        read = input.Read(buffer, 0, buffer.Length);
        output.Write(buffer, 0, read);
    }
}

Note that this is somewhat 'skeletal' and you should amend as required for your application of it.

Answer 4

Is it necessary to us FileStream? Because you can do this very easily with simple File Class like;

using System.IO;
string FileContent = File.ReadAllText(FilePathWhoseTextYouWantToCopy);
File.WriteAllText(FilePathToWhomYouWantToPasteTheText,FileContent);

Answer 5

using (var inputStream = File.OpenRead(@"C:\file1.txt"))
{
    using (var outputStream = File.OpenWrite(@"D:\file2.txt"))
    {
        int bufferLength = 128;
        byte[] buffer = new byte[bufferLength];
        int bytesRead = 0;

        do
        {
            bytesRead = inputStream.Read(buffer, 0, bufferLength);
            outputStream.Write(buffer, 0, bytesRead);
        }
        while (bytesRead != 0);
    }
}

Answer 6

If you are not keen at using Read/Write function of File , you can better try using Copy functionality

Easiest will be : 

      File.Copy(source_file_name, destination_file_name, true)

true--> for overwriting existing file,without "true" it will create a new file.But if the file already exists it will throw exception without "true" argument.

Answer 7

Use FileStream class, from System.IO.

[ComVisibleAttribute(true)]
public class FileStream : Stream

Answer 8

Have you checked that the reader is reading all the data? This MSDN page has an example that checks all the data is read:

    byte[] verifyArray = binReader.ReadBytes(arrayLength);
    if(verifyArray.Length != arrayLength)
    {
        Console.WriteLine("Error reading the data.");
        return;
    }

The other alternative is that you probably need to Flush the output buffer:

writer.Flush();