[C#] Easiest way to read from and write to files


Answers

In addition to File.ReadAllText, File.ReadAllLines, and File.WriteAllText (and similar helpers from File class) shown in another answer you can use StreamWriter/StreamReader classes.

Writing a text file:

using(StreamWriter writetext = new StreamWriter("write.txt"))
{
    writetext.WriteLine("writing in text file");
}

Reading a text file:

using(StreamReader readtext = new StreamReader("readme.txt"))
{
   string readMeText = readtext.ReadLine();
}

Notes:

  • You can use readtext.Close() instead of using, but it will not close file/reader/writer in case of exceptions
  • Be aware that relative path is relative to current working directory. You may want to use/construct absolute path.
  • Missing using/Close is very common reason of "why data is not written to file".
Question

There are a lot of different ways to read and write files (text files, not binary) in C#.

I just need something that is easy and uses the least amount of code, because I am going to be working with files a lot in my project. I only need something for string since all I need is to read and write strings.




It's good when reading to use the OpenFileDialog control to browse to any file you want to read. Find the code below:

Don't forget to add the following using statement to read files: using System.IO;

private void button1_Click(object sender, EventArgs e)
{
    if (openFileDialog1.ShowDialog() == DialogResult.OK)
    {
         textBox1.Text = File.ReadAllText(openFileDialog1.FileName);  
    }
}

To write files you can use the method File.WriteAllText.




@AlexeiLevenkov pointed me at another "easiest way" namely the extension method. It takes just a little coding, then provides the absolute easiest way to read/write, plus it offers the flexibility to create variations according to your personal needs. Here is a complete example:

This defines the extension method on the string type. Note that the only thing that really matters is the function argument with extra keyword this, that makes it refer to the object that the method is attached to. The namespace and class declarations are optional.

using System.IO;//File, Directory, Path

namespace Lib
{
    /// <summary>
    /// Handy string methods
    /// </summary>
    public static class Strings
    {
        /// <summary>
        /// Extension method to write the string Str to a file
        /// </summary>
        /// <param name="Str"></param>
        /// <param name="Filename"></param>
        public static void WriteToFile(this string Str, string Filename)
        {
            File.WriteAllText(Filename, Str);
            return;
        }

        // of course you could add other useful string methods...
    }//end class
}//end ns

This is how to use the string extension method, note that it refers automagically to the class Strings:

using Lib;//(extension) method(s) for string
namespace ConsoleApp_Sandbox
{
    class Program
    {
        static void Main(string[] args)
        {
            "Hello World!".WriteToFile(@"c:\temp\helloworld.txt");
            return;
        }

    }//end class
}//end ns

I would never have found this myself, but it works great, so I wanted to share this. Have fun!




FileStream fs = new FileStream(txtSourcePath.Text,FileMode.Open, FileAccess.Read);
using(StreamReader sr = new StreamReader(fs))
{
   using (StreamWriter sw = new StreamWriter(Destination))
   {
            sw.writeline("Your text");
    }
}