How to both Read/Write File in C#

Question

I want to both read and write to a file. this dont works

static void Main(string[] args)
        {
            StreamReader sr = new StreamReader(@"C:\words.txt");
            StreamWriter sw = new StreamWriter(@"C:\words.txt");
        }

How do both read and write file in C#?

Answer 1

You need a single stream, opened for both reading and writing.

FileStream fileStream = new FileStream(
      @"c:\words.txt", FileMode.OpenOrCreate, 
      FileAccess.ReadWrite, FileShare.ReadWrite));

Answer 2

How to: Read Text from a File

How to: Write Text to a File

Answer 3

var fs = File.Open("file.name", FileMode.OpenOrCreate, FileAccess.ReadWrite);
var sw = new StreamWriter(fs);
var sr = new StreamReader(fs);

...

fs.Close();
//or sw.Close();

The key thing is to open the file with the FileAccess.ReadWrite flag. You can then create whatever Stream/String/Binary Reader/Writers you need using the initial FileStream.

Answer 4

Don't forget the easy route:

    static void Main(string[] args)
    {
        var text = File.ReadAllText(@"C:\words.txt");
        File.WriteAllText(@"C:\words.txt", text + "DERP");
    }