Simple File IO in .NET

It is fairly easy to perform read/write options to files in .NET. There are three objects you might need:

1. FileStream
2. StreamReader, or
3. StreamWriter

There are 15 ways to use a FileStream object, but we only care about one. When we create a FileStream, we will give it a file name, a type file mode, and a type of file access. To read a file, we will specify FileMode.Open, to write a file we will specify FileMode.Create. As for file access, we will specify FileAccess.Read or FileAccess.Write, depending on whether we want to read or write!

Sample Code:

using System.IO;
using (FileStream fs = new FileStream(FILE_PATH, 
        	       FileMode.Open, FileAccess.Read)) {
    using (StreamReader sr = new StreamReader(fs)) {
        while (sr.Peek() != -1) {
            string aLine = sr.ReadLine();
        }
    }
}

Notes:

• FILE_PATH is assumed to be a string constant containing the path to your file
• I utilized the 'using' keyword to ensure that my objects are disposed after I'm don
• Note that .NET unfortunately utilizes the keyword 'using' in two separate contexts, one meaning to import a library, the other meaning to dispose of a variable once it has gone out of scope.
• StreamReader.Peek() looks at the next entry in the file without consuming it, thus it is a safe way to detect end of file conditions.

Writing to a file utilizes almost exactly the same techniques, but with different FileMode and FileAccess.

Take a look at this sample:

using System.IO;
using (FileStream fs = new FileStream(FILE_PATH, 
                        FileMode.Create, FileAccess.Write)) {
    using (StreamWriter sw = new StreamWriter(fs)) {
        sw.WriteLine("This is my file contents");
    }
}