StreamWriter Class

StreamWriter is designed for character output in a particular encoding, whereas classes derived from Stream are designed for byte input and output.

StreamWriter defaults to using an instance of UTF8Encoding unless specified otherwise. This instance of UTF8Encoding is constructed without a byte order mark (BOM), so its GetPreamble method returns an empty byte array. The default UTF-8 encoding for this constructor throws an exception on invalid bytes. This behavior is different from the behavior provided by the encoding object in the Encoding.UTF8 property. To specify a BOM and determine whether an exception is thrown on invalid bytes, use a constructor that accepts an encoding object as a parameter, such as StreamWriter(String, Boolean, Encoding) or StreamWriter.

By default, a StreamWriter is not thread safe. See TextWriter.Synchronized for a thread-safe wrapper.

For a list of common I/O tasks, see Common I/O Tasks.

The following example shows how to use a StreamWriter object to write a file that lists the directories on the C drive, and then uses a StreamReader object to read and display each directory name. A good practice is to use these objects in a using statement so that the unmanaged resources are correctly disposed. The using statement automatically calls Dispose on the object when the code that is using it has completed.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace StreamReadWrite
{
    class Program
    {
        static void Main(string[] args)
        {
            // Get the directories currently on the C drive.
            DirectoryInfo[] cDirs = new DirectoryInfo(@"c:\").GetDirectories();

            // Write each directory name to a file. 
            using (StreamWriter sw = new StreamWriter("CDriveDirs.txt"))
            {
                foreach (DirectoryInfo dir in cDirs)
                {
                    sw.WriteLine(dir.Name);

                }
            }

            // Read and show each line from the file. 
            string line = "";
            using (StreamReader sr = new StreamReader("CDriveDirs.txt"))
            {
                while ((line = sr.ReadLine()) != null)
                {
                    Console.WriteLine(line);
                }
            }
        }
    }
}

.NET Framework

.NET Framework Client Profile

Portable Class Library

.NET for Windows Store apps

Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference

Other Resources