how to add a string to existing text file c# code example

Example 1: c# append to file

File.AppendAllText(@"c:\path\file.txt", "text content" + Environment.NewLine);

Example 2: streamwriter append text

using (FileStream fs = new FileStream(fileName,FileMode.Append, FileAccess.Write))
 using (StreamWriter sw = new StreamWriter(fs))
 {
    sw.WriteLine(something);
 }