Create a .txt file if doesn't exist, and if it does append a new line

Use the correct constructor:

else if (File.Exists(path))
{
    using(var tw = new StreamWriter(path, true))
    {
        tw.WriteLine("The next line!");
    }
}

string path = @"E:\AppServ\Example.txt";
File.AppendAllLines(path, new [] { "The very first line!" });

See also File.AppendAllText(). AppendAllLines will add a newline to each line without having to put it there yourself.

Both methods will create the file if it doesn't exist so you don't have to.

• File.AppendAllText
• File.AppendAllLines

string path=@"E:\AppServ\Example.txt";

if(!File.Exists(path))
{
   File.Create(path).Dispose();

   using( TextWriter tw = new StreamWriter(path))
   {
      tw.WriteLine("The very first line!");
   }

}    
else if (File.Exists(path))
{
   using(TextWriter tw = new StreamWriter(path))
   {
      tw.WriteLine("The next line!");
   }
}