Console.SetIn() Method in C#

The Console.SetIn() method is used to set the In property of the specified StreamReader object i.e. it redirects the standard input from the console to the input file. Since the console is set with this StreamReader object, the ReadLine() method can be called to read the contents of the file, line by line.

Syntax: public static void SetIn (System.IO.StreamReader newIn);

Parameter:
newIn: It is a stream which is the new standard input.

Exceptions:

• ArgumentNullException: If the newIn is null.
• SecurityException: If the caller does not have the required permission.

Example: In this example, the SetIn() method is used to set the StreamReader object to the console, and the file’s content will be read, stored and printed.

Text File Used:

// C# program to demonstrate SetIn() method
using System;
using System.IO;

class GFG {

    // Main Method
    static void Main()
    {

        // Create a string to get
        // data from the file
        string geeks = " ";

        // creating the StreamReader object
        // and set it to the desired
        // text file
        using(StreamReader gfg = new StreamReader("D:\\out.txt"))
        {

            // setting the StreamReader
            // object to the Console
            Console.SetIn(gfg);

            string l;

            // Reading the contents of the file into l
            while ((l = Console.ReadLine()) != null)
            {
                geeks = geeks + l;
            }

            // Printing the file contents
            // appended to "Hello "
            Console.WriteLine("Hello " + geeks);

            // Waiting for user input
            // to exit the program
            Console.ReadKey();
        }
    }
}

Output:

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.console.setin?view=netframework-4.7.2#System_Console_SetIn_System_IO_TextReader_