Reading and Writing Text to Files - Page 1

Files are more than the documents you create in a word processor, images you design, source files you write, etc. They are not restricted to things you create or read, for almost everything you do on your computer directly or indirectly involves manipulating files. To view this HTML page, your browser received a file filled with HTML text. Your operating system uses a huge file to cache often-used pieces of data. When you compile your applications, the end result is a series of files that you as a human cannot read with a standard text editor.

More often than not, it is programs that are the intended readers for many files, and many programs write their own files in the background for various reasons. In this tutorial, you will learn how to write programs that read text from files and write text back to files using the StreamReader and StreamWriter Classes.

How Files Are Read/Written
In most operating systems, a file is associated with a particular application designated to read it. When reading a file, an application takes the collection of data and loads it into memory for further processing. When an application is said to read a file, the file's contents may loaded sequentially in fixed chunks, or the entire file may be loaded into memory and read in bulk. These details aren't too important for us, because the .NET classes we use take care of a lot of these details for us, but it is good to have a brief idea of what is possible beyond what this tutorial will cover.

Reading Files
To read a file, you need to know only the path of a file. Once you have the path to a file, you load the file into memory until there is nothing more to load. To facilitate this, you have the System.IO namespace's StreamReader class that provides a lot of the functionality needed to read a file for you.

First, find a text file. If you cannot find a text file, copy and paste the following Dave Barry quote into Notepad and save it into an easily accessible location:

In 1765, Parliament passed the Stamp Act, which, as any American high school student can tell you, was an act that apparently had something to do with stamps. - Dave Barry

For this example, I saved the above quote on my Desktop and called it quote.txt. With your text file set, the following code sample shows you how to read a file from your drive:

StreamReader reader = new StreamReader("C:\\Users\\Kirupa\\Desktop\\quote.txt");

 

string readerLine = reader.ReadLine();

 

while (readerLine != null)

{

Console.WriteLine(readerLine);

readerLine = reader.ReadLine();

}

When I run through the above code, I see each line from my quote.txt file displayed in the console:

[ the Console output ]

In the next page, I will go through the code line-by-line and provide any interesting details and alternative approaches.

Onwards to the next page!

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