How to read a secret from command line

Summary: A sample of C# code illustrating how to read a masked secret value entered via a console.

The following function can be used to read a secret value, such as a password from a command line:

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/// <summary> /// Reads a secret from command line masking the characters entered by the user. /// </summary> /// <param name="prompt"> /// Prompt to be displayed for the user (e.g. "Enter password: "). If not specified, the prompt will not be displayed. /// /// <param name="mask"> /// The masking character. /// /// <returns> /// The string entered by the user. /// </returns> private static string GetSecret (     string prompt = null,     char mask = '*' ) {     // Input codes requiring special handling.     const int ENTER         = 13;     const int BACKSPACE     = 8;     const int CTRLBACKSPACE = 127;     const int ESC           = 27;       // Character codes that must be ignored.     int[] FILTERED = { 0, 9, 10 /*, 32 space, if you care */ };       var secret = new System.Collections.Generic.Stack<char>();     char chr = (char)0;       // If the prompt was specified, show it to the user.     if (!String.IsNullOrEmpty(prompt))       Console.Write(prompt);           // Continue reading entered keys until user presses ENTER or ESC.     while (((chr = System.Console.ReadKey(true).KeyChar) != ENTER) && (chr != ESC))     {         if (chr == BACKSPACE)         {             if (secret.Count > 0)             {                 System.Console.Write("\b \b");                 secret.Pop();             }         }         else if (chr == CTRLBACKSPACE)         {             while (secret.Count > 0)             {                 System.Console.Write("\b \b");                 secret.Pop();             }         }         else if (chr == ESC)         {             while (secret.Count > 0)             {                 System.Console.Write("\b \b");                 secret.Pop();             }         }         else if (FILTERED.Count(x => chr == x) > 0)         {         }         else         {             secret.Push((char)chr);             System.Console.Write(mask);         }     }       System.Console.WriteLine();       return new string(secret.Reverse().ToArray()); }   </char>