FileStream

In .NET we often access files through streams. We can place one stream on top of another (usually with "using" statements).

For the FileStream, we often need to use another stream (like StreamWriter) on top of it. We can do many things with a file using a FileStream.

Example

Here we get a FileStream using the File.Create method. Other methods, like File.Open or File.OpenText can be used to get a FileStream.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Use FileStream with File.Create.
        // ... Pass FileStream to a StreamWriter and write data to it.
        using (FileStream fileStream =
            File.Create(@"C:\programs\example1.txt"))
        using (StreamWriter writer = new StreamWriter(fileStream))
        {
            writer.WriteLine("Example 1 written");
        }
        Console.WriteLine("DONE");
    }
}
DONE

Length

FileStream has a Length property that will return the length of a file in bytes. This is bytes, not chars, meaning some Unicode strings will have different lengths.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Open existing text file with File.OpenRead
        using (FileStream fileStream = File.OpenRead("TextFile1.txt"))
        {
            // Use Length property to get number of bytes
            long length = fileStream.Length;
            // Write length to console
            Console.WriteLine("Length: {0}", length);
        }
    }
}

Some notes

It is important to understand how streams can be used together to develop complex (and custom) file handling routines in C#. Many stream types are available.

Stream types, methods

Streams can act on a physical file (as with FileStream) or a logical piece of memory (as with MemoryStream). We can act upon these streams in a similar way.

Understanding the dynamics of streams is important. For more complex tasks, a FileStream is often useful as many streams are combined in methods, one acting upon another.