How do I convert a Console.Readkey to an int c#

Question

I am trying to convert a user input key to an int, the user will be entering a number between 1 and 6.

This is what i have so far sitting inside a method, its not working, yet throwing a format exception was unhandled.

        var UserInput = Console.ReadKey();



        var Bowl = int.Parse(UserInput.ToString());

        Console.WriteLine(Bowl);

       if (Bowl == 5)
        {
            Console.WriteLine("OUT!!!!");
        }
        else
        {
            GenerateResult();
        }

    }

Thanks for your help!

Answer 1

Simply said you are trying to convert System.ConsoleKeyInfo to an int .

In your code, when you call UserInput.ToString() what you get is the string that represents the current object , not the holding value or Char as you expect.

To get the holding Char as a String you can use UserInput.KeyChar.ToString()

Further more ,you must check ReadKey for a digit before you try to use int.Parse method. Because Parse methods throw exceptions when it fails to convert a number.

So it would look like this,

int Bowl; // Variable to hold number

ConsoleKeyInfo UserInput = Console.ReadKey(); // Get user input

// We check input for a Digit
if (char.IsDigit(UserInput.KeyChar))
{
     Bowl = int.Parse(UserInput.KeyChar.ToString()); // use Parse if it's a Digit
}
else
{
     Bowl = -1;  // Else we assign a default value
}

And your code :

int Bowl; // Variable to hold number

var UserInput = Console.ReadKey(); // get user input

int Bowl; // Variable to hold number

// We should check char for a Digit, so that we will not get exceptions from Parse method
if (char.IsDigit(UserInput.KeyChar))
{
    Bowl = int.Parse(UserInput.KeyChar.ToString());
    Console.WriteLine("\nUser Inserted : {0}",Bowl); // Say what user inserted 
}
else
{
     Bowl = -1;  // Else we assign a default value
     Console.WriteLine("\nUser didn't insert a Number"); // Say it wasn't a number
}

if (Bowl == 5)
{
    Console.WriteLine("OUT!!!!");
}
else
{
    GenerateResult();
}

Answer 2

Similarly:

ConsoleKeyInfo info = Console.ReadKey();
int val;
if (int.TryParse(info.KeyChar.ToString(), out val))
{
    Console.WriteLine("You pressed " + val.ToString());
}

Answer 3

Here is an extension class that makes it a little more extensible and not just for integers:

using System;

/// <summary>
/// Extension methods for <see cref="ConsoleKeyInfo"/>
/// </summary>
public static class ConsoleKeyInfoExtensions
{
    /// <summary>
    /// Attempts to cast the <see cref="ConsoleKeyInfo.KeyChar"/> value from the <paramref name="instance"/> to <typeparamref name="T"/>.
    /// </summary>
    /// <typeparam name="T">The generic type to cast to.</typeparam>
    /// <param name="instance">The <see cref="ConsoleKeyInfo"/> to extract the value from</param>
    /// <returns>Returns the value in the <see cref="ConsoleKeyInfo.KeyChar"/> as <typeparamref name="T"/></returns>
    /// <exception cref="InvalidCastException">If there is an issue with the casting.  For example, boolean is not valid.</exception>
    /// <exception cref="ArgumentNullException">If the <paramref name="instance"/> is null.</exception>
    public static T GetValue<T>(this ConsoleKeyInfo instance)
    {
        if (instance == null)
            throw new ArgumentNullException(nameof(instance));

        var stringValue = instance.KeyChar.ToString();

        try
        {
            return (T)Convert.ChangeType(stringValue, typeof(T));
        }
        catch
        {
            throw new InvalidCastException($"Unable to cast a {nameof(ConsoleKeyInfo.KeyChar)} to a type of {typeof(T).FullName}.");
        }
    }
}

~ Cheers

Answer 4

There are ConsoleKeys for numerical values. ConsoleKey.D5 is for 5.

The block of code can be re-written as -

var bowl = -1;
var userInput = Console.ReadKey();
if(userInput.Key == ConsoleKey.D5)
{
  bowl = 5; 
}

Answer 5

这是没有错误检查的简短答案。

int.Parse(Console.ReadKey().KeyChar.ToString());