Check out example codes for "c# append text to file". It will help you in understanding the concepts better.

Code Example 1

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

Code Example 2

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

Code Example 3

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

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