File.ReadAllText(String) Method in C# with Examples

File.ReadAllText(String) is an inbuilt File class method that is used to open a text file then reads all the text in the file and then closes the file.
Syntax:

public static string ReadAllText (string path);

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

• path: This is the specified file to open for reading.

Exceptions:

• 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.
• IOException: An I/O error occurred while opening the file.
• UnauthorizedAccessException: The path specified a file that is read-only. OR this operation is not supported on the current platform. OR the path specified a directory. OR the caller does not have the required permission.
• FileNotFoundException: The file specified in the path was not found.
• NotSupportedException: The path is in an invalid format.
• SecurityException: The caller does not have the required permission.

Return Value: Returns a string containing all the text in the file.
Below are the programs to illustrate the File.ReadAllText(String) method.
Program 1: Initially, a file file.txt is created with some contents shown below-

C#

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

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

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

        // Calling the ReadAllText() function
        string readText = File.ReadAllText(path);

        // Printing the file contents
        Console.WriteLine(readText);
    }
}

Output:

GFG
gfg
Geeks
GeeksforGeeks
geeksforgeeks

Program 2: Initially, no file was created. Below code itself create a file file.txt with some specified contents.

C#

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

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

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

        // Adding below contents to the file
        string[] createText = { "GFG", "is", "a", "CS", "portal" };
        File.WriteAllLines(path, createText);

        // Calling the ReadAllText() function
        string readText = File.ReadAllText(path);

        // Printing the file contents
        Console.WriteLine(readText);
    }
}

Output:

GFG
is
a
CS
portal