Console.ReadLine() not keeping console open in C#

Question

I'm learning C# (VS 2012 Professional) and in the following example, the console window isn't staying open even though the Console.ReadLine() method is the last instruction in the code block:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace testing
{
    class Program
    {
    static void Main(string[] args)
    {

        // fahrenheit conversion example
        Console.Write("Enter temp in fahrenheit: ");
        double fahrenheit = Console.Read();
        double celsius = (fahrenheit - 32.0) * (5.0 / 9.0);
        Console.WriteLine("Celsius is: " + celsius);
        Console.ReadLine();

    }

    }
}

Is there an intricacy I am overlooking in the implementation of the Console.ReadLine() method or perhaps a conflicting piece of code in the code block?

Steve · Accepted Answer · 2013-07-20T13:08:08.257

8

Probably you type the value for the fahrenheit variable and then press Return (Enter). This will get the value in the Read call and the Enter in the ReadLine.

Change to

Console.Write("Enter temp in fahrenheit: ");
double fahrenheit;
string userInput = Console.ReadLine();
if(double.TryParse(userInput, out fahrenheit))
{
    double celsius = (fahrenheit - 32.0) * (5.0 / 9.0);
    Console.WriteLine("Celsius is: " + celsius);
}
else
{
    Console.WriteLine("Non a valid double value");
}
Console.ReadLine();

Also, the Console.ReadLine, unlike the Console.Read, returns a string and thus you need to parse and convert to a double before trying to use it. This could be done with double.TryParse that will return false when the user doesn't type a valid numeric double

Another drawback for Console.Read is that you need to call it in a loop to read all characters typed by the user till the Enter. If you try to convert 12.8 you need a completely different code to go with Console.Read. (Look at the MSDN example in the link above)

edited Jul 20 '13 at 13:08

answered Jul 20 '13 at 12:35

Steve

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2

+1 - Beat me to it, Changing the last to `ReadKey`, also works. (was testing although readline is needed for first) – Sayse Jul 20 '13 at 12:37
Double.Parse required `Console.ReadLine()` returns string – Sriram Sakthivel Jul 20 '13 at 12:38
`Cannot implicitly convert type 'string' to 'double'` raised possibly because a double can't be entered in ReadLine()? But it can be entered in `Read()`. – user1063287 Jul 20 '13 at 12:38
@SriramSakthivel, well, you are right but then it is better to use Double.TryParse and avoid the exception – Steve Jul 20 '13 at 12:39
1

Also simply changing the `ReadLine()` call to `ReadKey()` works. – Sri Harsha Chilakapati Jul 20 '13 at 12:45
Confirmed, using the original code and changing the last `ReadLine()` to `ReadKey()` also allows the console window to stay open. – user1063287 Jul 20 '13 at 12:54
Yes, but please read the docs on Console.Read from MSDN (link above). It returns an Integer not a Double and you need a loop to get all the values typed by the user (For example 12.8 requires 4 Console.Read call) – Steve Jul 20 '13 at 13:05

score 0 · Answer 2 · answered Jul 20 '13 at 13:12

Console.Read() "Reads the next character from the standard input stream". This includes the Enter key. It returns an integer so, for Enter, would return 13.

Console.ReadLine() "Reads the next line of characters from the standard input stream". This includes the Enter key (the newline character) but this character is discarded. it returns a string.

Console.ReadKey() "Obtains the next character or function key pressed by the user". That is, it ignores whatever is left in the input stream and waits for the next key-press.

So you might use Read() within a loop to read individual characters, stopping when a certain character is read, or use ReadLine() to read, and then parse, the complete line entered by the user. But using both Read() and ReadLine() in the same code can be problematic.

score 0 · Answer 3 · answered Mar 25 '14 at 21:25

0

Just press Ctrl+F5 to run the code.

answered Mar 25 '14 at 21:25

Ashraf Sada

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Console.ReadLine() not keeping console open in C#

3 Answers3