Simple I/O (reading a text file)

Question

I looked online for a simple example of file reading and writing. Being a python graduate and moving into C# was a big step for me, but I do really love the language.

I've seen people do file I/O with StringReader, FileSystem, and I hear that Stream is also used. As a beginner to the language, one who doesn't know too many complicated concepts (but has the basic stuff down, methods, classes, functions) how would I go about reading a file correctly? I see people using the "using" keyword, and then treating it like a class or method. I have no clue what thats all about. I'm looking for something like

    FileSystem() f = file.read("test.txt")
    f.DoStuff()

In python, it was really easy to use a dictionary stored in another file. All I had to do was:

    import Dict.py
    # Now i have access to all of Dict's dictionaries. We'll say the name of one
    # of the dictioanries is "f".

    print Dict.f[1] # Or whatever. Now i can use the dictionary f like it was local.

My goal is to make a hangman game. I'm trying to pick a random word from a list of words (English dictionary) and have them guess that word, but I don't know how to do such things like read the file, and import its contents. Again, as simple as you can make it so a beginner can understand would be really helpful. Thanks a million!

Answer 1

Here are some of the most important classes to do IO in C#:

Raw binary IO

• Stream: it's the base class for all classes that represent a sequential stream of bytes. The stream can be read-only, write-only or read-write. It provides methods like Read, Write and Seek. Keep in mind that a stream is used to access raw, binary data; depending on what you want to do, it might not be convenient to use it directly.
  • FileStream: a stream to read and/or write data in a file.
  • MemoryStream: a stream to read and write data in memory.

Text IO

• TextReader: it's the base class for all classes used to read a sequence of characters. It provides methods like Read, ReadLine, and ReadToEnd.

  • StreamReader: a TextReader that reads text from a Stream. A StreamReader always has an Encoding (UTF-8, ASCII, etc) that specifies how to convert the binary data from the stream into text.
  • StringReader: a TextReader that reads text from a String (useful to process an in-memory string as if it was the content of a file)

• TextWriter: it's the base class for all classes used to write a sequence of characters. It provides methods like Write and WriteLine.

  • StreamWriter: a TextWriter that writes text to a Stream. Like StreamReader, it has an Encoding that specifies how to convert the text to binary data.
  • StringWriter: a TextWriter that writes text to a StringBuilder.

The .NET framework also provides a helper class named File for simplified IO operations:

• the ReadAllBytes method returns all the content of a file as an array of bytes
• the ReadAllText method returns all the content of a file as a string
• the ReadAllLines method returns all the lines of text from a file as an array of strings
• the WriteAllBytes method writes the specified array of bytes to a file (replacing the existing content)
• the WriteAllText method writes the specified string to a file (replacing the existing content)
• the WriteAllLines method writes the specified lines of text to a file (replacing the existing content)

For more details, read the documentation of the System.IO namespace on MSDN

Answer 2

C# has nice built-in methods that allows you to easily read & manipulate file contents. For example if you want to read all the lines from a file you can simply use File.ReadAllLines method:

var lines = File.ReadAllLines("your file path");

If you want to exclude some lines, you could use File.ReadLines method with Linq:

var filteredLines = File.ReadLines("your file path")
                    .Where(line => yourCondition)
                    .ToArray();

Those are just two simple example. See the documentation for more details:

1. File Class
2. File and Stream I/O