How to avoid Console.Write after Ctrl-C during Console.ReadLine?

Question

I have a small .NET console program that asks for SQL credentials (login, password). The problem is that if I key Ctrl-C during login prompt (string userId = Console.ReadLine(); below), the program stops but "password:" prompt is written to the console. Relevant fragment:

Console.Write("login: ");
string userId = Console.ReadLine();
    
Console.Write("password: ");

Output on Ctrl-C during login prompt:

login: password:

How can I avoid executing subsequent the Console.Write("password: "); after exiting with Ctrl-C?

UPDATE 1: CancelKeyPress event handler doesn't help. At least for me, it works for Console.ReadKey, but not for Console.ReadLine: password prompt is still written.

UPDATE 2: If there is Write/WriteLine after null-check block, it's still executed on my machine (Win10, VS2019). So, the question in fact remains. Current workaround - ReadKey.

Does this answer your question? [How do I trap ctrl-c (SIGINT) in a C# console app](https://stackoverflow.com/questions/177856/how-do-i-trap-ctrl-c-sigint-in-a-c-sharp-console-app) — Kraego, Sep 13 '21 at 18:39
I ran this code on my machine and the process exits immediately after I press **Ctrl-C**. — AgentFire, Sep 18 '21 at 17:30

Kraego · Accepted Answer · 2021-09-19T17:22:03.623

0

As AgentFire mentioned add input validation.

    class Program
    {
        static void Main()
        {
            Console.Write("login: ");
            string userId = Console.ReadLine();

            if (string.IsNullOrWhiteSpace(userId))
            {
                Environment.Exit(-1);
            }
            Console.Write("password: ");
            ....
        }

    }

edited Sep 19 '21 at 17:22

answered Sep 18 '21 at 16:18

Kraego

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Thank you, but Write after check still executes for me (added a note). Apparently, I'll move on with ReadKey. – guest Sep 19 '21 at 17:00
One way, could be to invert the logic as i did in the edit of my answer - end program when input is null or empty (maybe not so good for diagnostics). Or add checks for all inputs, or as you mentioned use ReadKey .... – Kraego Sep 19 '21 at 17:24

score 0 · Answer 2 · answered Sep 18 '21 at 17:33

0

If your code indeed continues to run after you press Ctrl-C (which it doesn't on my machine for some reason), I would bet ten bucks that your userId variable would be null, instead of the usual empty string (if you input nothing and press Enter).

So, just check for null.

answered Sep 18 '21 at 17:33

AgentFire

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Thank you, but Write after check still executes for me (added a note). Apparently, I'll move on with ReadKey. – guest Sep 19 '21 at 17:01

How to avoid Console.Write after Ctrl-C during Console.ReadLine?

2 Answers2