Reading and Writing Text to Files - Page 2

In the previous page I provided some minor background information on what files are, and more importantly, you got to see an example of the code used to read a text file. In this page, I will explain what each line of code does and begin talking about how to write text files.

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

First, let's create a reader object that is of type StreamReader. As part of the StreamReader constructor, I am passing in the path to my text file. Notice that the folders in the path are not separated by single slashes as  C:\Users\Kirupa\Desktop\quote.txt. Instead, the folder paths are delimited by double slashes because of the way strings in .NET are parsed. You will receive an error if you attempt to keep the path using single-slashes.

Another common way to deal with string-based paths is by using the @ symbol. The @ symbol allows you to treat strings literally without having them be parsed. With this modification, our code would look like the following:

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

Notice that I am no longer using double-slashes because the @ symbol before our quotes informs the compiler to not parse the string.

string readerLine = reader.ReadLine();

Next, I create a new string variable called readerLine. I initialize readerLine to the first line from our text file by using the reader object's ReadLine() method.

while (readerLine != null)

{

Console.WriteLine(readerLine);

readerLine = reader.ReadLine();

}

The above loop is where the main reading of your file takes place. The loop will run as long as our readerLine variable still holds some text from our text file. As you progress through the loop, you set the readerLine variable equal to the next line from our text file by using the ReadLine() method.

Once you reach the end of your text file, reader.ReadLine() will return a null because there are no more lines of text to show. Once the null value is returned, our readerLine variable also equals null, and if you recall, our loop only loops when readerLine is not equal to null!

Reading a file is fairly straightforward. The only thing to watch out for is making sure you are ending your loop properly. Common mistakes I've made include forgetting to initialize the readerLine variable to the first line of text prior to looping. That causes your loop to break immediately. Another mistake I made is forgetting to set the readerLine variable equal to the next line inside the loop.

Besides what I listed above, reading files should is pretty straightforward. Of course, reading files is only half the fun! In the next page, you will learn how to use code to write text to a file.

Onwards to the next page!

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