Reading and Writing Text to Files - Page 3

In the previous page, you learned what each line of code used in our 'reading a file' example does. In this page, let's learn about the other big part of this tutorial - writing files.

Writing Files
In this section, you will learn how to take string data and write it to a file. While writing a file seems more complicated, it actually takes fewer steps than when you are reading a file.

To write a file, all you really need to do is specify the location of your saved file and have some text that you need to write:

StreamWriter writer = new StreamWriter("C:\\Users\\Kirupa\\Desktop\\foo.txt");

writer.WriteLine("Hello world!");

writer.Close();

Let's dive right into what the code actually does:

StreamWriter writer = new StreamWriter("C:\\Users\\Kirupa\\Desktop\\foo.txt");

In this line, I create a new StreamWriter object called writer. The StreamWriter constructor takes a file as an argument. The file you specify is where your data will be written to. If the file you specify does not exist, that file will be created automatically for you. If the file already exists, and no other program is currently accessing it, you will overwrite it.

writer.WriteLine("Hello world!");

In this line, you specify the text to write to your file. The WriteLine method can take a string as its argument, and in the above line, I am passing in the text "Hello World!"

writer.Close();

In this line, we commit the change we made by closing the connection. If you do not close the StreamWriter object, any text you write or modifications you make will not be saved.

As you can see, writing a line of text to a file is not too complicated. The main thing to remember is that there is no functionality to append data to the end of a file. Any data you add overwrites the existing file with the new data, so unless you want to lose your data, make sure to read and store the existing data first.

Checking if a File Exists
You cannot read a file that does not exist, and you may not want to overwrite an existing file. Both of these scenarios can be avoided by checking if the file you are writing to exists first. You can check if a File exists by using File.Exists():

string filePath = "C:\\Users\\Kirupa\\Desktop\\foo.txt");

 

if (File.Exists(filePath))

{

// File exists

}

else

{

// File does not exist

}

In the next page, I will provide some more information concerning checking how a file exists and wrap it up with a brief discussion on the asynchronous properties of the StreamReader and StreamWriter classes.

Onwards to the next page!

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