File.OpenText() Method in C# with Examples

File.OpenText(String) is an inbuilt File class method which is used to open an existing UTF-8 encoded text file for reading.
Syntax:

public static System.IO.StreamReader OpenText (string path);

Parameter: This function accepts a parameter which is illustrated below:  

• path: This is the specified text file which is going to be opened for reading.

Exceptions:

• UnauthorizedAccessException: The caller does not have the required permission.
• ArgumentException: The path is a zero-length string, contains only white space, or one or more invalid characters as defined by InvalidPathChars.
• ArgumentNullException: The path is null.
• PathTooLongException: The specified path, file name, or both exceed the system-defined maximum length.
• DirectoryNotFoundException: The specified path is invalid.
• FileNotFoundException: The file specified in the path was not found.
• NotSupportedException: The path is in an invalid format.

Return Value: Returns a StreamReader on the specified path.
Below are the programs to illustrate the File.OpenText(String) method.
Program 1: Before running the below code, a text file file.txt is created with some contents shown below-

Below code open the text file file.txt for reading.

C#

// C# program to illustrate the usage
// of File.OpenText(String) method

// Using System and System.IO
// namespaces
using System;
using System.IO;

class Test {
    public static void Main()
    {
        // Specifying a text file
        string path = @"file.txt";

        // Opening the file for reading
        using(StreamReader sr = File.OpenText(path))
        {
            string s = "";
            while ((s = sr.ReadLine()) != null) {
                // printing the file contents
                Console.WriteLine(s);
            }
        }
    }
}

Executing:

GeeksforGeeks

Program 2: Initially, a file file.txt is created with some contents shown below-

This below code will overwrite the file contents with other specified contents then final contents will be printed.

C#

// C# program to illustrate the usage
// of File.OpenText(String) method

// Using System and System.IO
// namespaces
using System;
using System.IO;

class Test {
    public static void Main()
    {
        // Specifying a text file
        string path = @"file.txt";

        // Checking the existence of file
        if (File.Exists(path)) {
            using(StreamWriter sw = File.CreateText(path))
            {
                // Overwriting the file with below
                // specified contents
                sw.WriteLine("GFG is a CS portal.");
            }
        }

        // Opening the file for reading
        using(StreamReader sr = File.OpenText(path))
        {
            string s = "";
            while ((s = sr.ReadLine()) != null) {
                // printing the overwritten content
                Console.WriteLine(s);
            }
        }
    }
}

Executing:

GFG is a CS portal.