File.AppendText() Method in C# with Examples Last Updated : 28 Apr, 2025 Summarize Comments Improve Suggest changes Share Like Article Like Report File.AppendText() is an inbuilt File class method which is used to create a StreamWriter that appends UTF-8 encoded text to an existing file else it creates a new file if the specified file does not exist.Syntax: public static System.IO.StreamWriter AppendText (string path); Parameter: This function accepts a parameter which is illustrated below: path: This is the file where UTF-8 encoded texts are going to be appended. The file is created if it doesn't already exist. Exceptions UnauthorizedAccessException: The caller does not have the required permission.ArgumentException: The path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.ArgumentNullException: The path is null.PathTooLongException: The given path, file name, or both exceed the system-defined maximum length.DirectoryNotFoundException: The given path is invalid i.e, the directory doesn't exist or it is on an unmapped drive.NotSupportedException: The path is in an invalid format. Return Value: Returns a stream writer that appends specified UTF-8 encoded texts to the specified file or to a new file.Below are the programs to illustrate the File.AppendText() method.Program 1: Before running the below code, a file file.txt is created with some contents which is shown below: CSharp // C# program to illustrate the usage // of File.AppendText() method // Using System, System.IO namespaces using System; using System.IO; class GFG { // Main method public static void Main() { // Creating a file string myfile = @"file.txt"; // Appending the given texts using(StreamWriter sw = File.AppendText(myfile)) { sw.WriteLine("Gfg"); sw.WriteLine("GFG"); sw.WriteLine("GeeksforGeeks"); } // Opening the file for reading using(StreamReader sr = File.OpenText(myfile)) { string s = ""; while ((s = sr.ReadLine()) != null) { Console.WriteLine(s); } } } } Executing: mcs -out:main.exe main.cs mono main.exe Geeks Gfg GFG GeeksforGeeks After running the above code, above output is shown and the existing file file.txt becomes like below: Program 2: Initially, no file is created and hence below code itself create a file named as file.txt CSharp // C# program to illustrate the usage // of File.AppendText() method // Using System, System.IO namespaces using System; using System.IO; class GFG { // Main method public static void Main() { // Creating a file string myfile = @"file.txt"; // Checking the above file if (!File.Exists(myfile)) { // Creating the same file if it doesn't exist using(StreamWriter sw = File.CreateText(myfile)) { sw.WriteLine("GeeksforGeeks"); sw.WriteLine("is"); sw.WriteLine("a"); } } // Appending the given texts using(StreamWriter sw = File.AppendText(myfile)) { sw.WriteLine("computer"); sw.WriteLine("science"); sw.WriteLine("portal."); } // Opening the file for reading using(StreamReader sr = File.OpenText(myfile)) { string s = ""; while ((s = sr.ReadLine()) != null) { Console.WriteLine(s); } } } } Executing: mcs -out:main.exe main.cs mono main.exe GeeksforGeeks is a computer science portal. After running the above code, a new file file.txt is created which is shown below: Comment More infoAdvertise with us K Kanchan_Ray Follow Improve Article Tags : C# CSharp-File-Handling Similar Reads C# Tutorial C# (pronounced "C-sharp") is a modern, versatile, object-oriented programming language developed by Microsoft in 2000 that runs on the .NET Framework. Whether you're creating Windows applications, diving into Unity game development, or working on enterprise solutions, C# is one of the top choices fo 4 min read Introduction to .NET Framework The .NET Framework is a software development framework developed by Microsoft that provides a runtime environment and a set of libraries and tools for building and running applications on Windows operating systems. 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