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code1:

using System;
using System.IO;

class Test 
{
    public static void Main() 
    {
        // Create an instance of StreamWriter to write text to a file.
        // The using statement also closes the StreamWriter.
        using (StreamWriter sw = new StreamWriter("TestFile.txt")) 
        {
            // Add some text to the file.
            sw.Write("This is the ");
            sw.WriteLine("header for the file.");
            sw.WriteLine("-------------------");
            // Arbitrary objects can also be written to the file.
            sw.Write("The date is: ");
            sw.WriteLine(DateTime.Now);
        }
    }
}

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code2:

using System;
using System.IO;
public class TextToFile 
{
    private const string FILE_NAME = "MyFile.txt";
    public static void Main(String[] args) 
    {
        if (File.Exists(FILE_NAME)) 
        {
            Console.WriteLine("{0} already exists.", FILE_NAME);
            return;
        }
        using (StreamWriter sw = File.CreateText(FILE_NAME))
        {
            sw.WriteLine ("This is my file.");
            sw.WriteLine ("I can write ints {0} or floats {1}, and so on.", 
                1, 4.2);
            sw.Close();
        }
    }
}