How do I convert a string to double using input?

Question

I want to ask a user to input a number in a string type (because that's the only way in C#) and then convert it into a double type.

private static string InputDouble(double prompt)
{
    Console.WriteLine("{0:s}: ", prompt);
    return Convert.ToDouble(Console.ReadLine());
}

I hope anyone has a solution for this.

What is problem? (other than: your method should return double). — isaeid, Jan 03 '19 at 10:12
Remember to catch exceptions like `FormatException` for example. — Valentin P, Jan 03 '19 at 10:14
@ValentinP Which is a really bad appraoch to prevent whrongly formatted input from being parsed. Better would be using `TryParse`. Don´t catch exceptions when you can avoid them in the first place. — MakePeaceGreatAgain, Jan 03 '19 at 10:15
I would not use a try/catch too. `TryParse` is a way to handle exceptions no ? :) — Valentin P, Jan 03 '19 at 10:17

Transcendent · Answer 1 · 2019-01-03T10:15:06.823

1

You can use Double's TryParse method:

public Double? StringToDouble(String input){
    if(Double.TryParse(input, out Double d)) {
        Console.WriteLine("The double value is {0}", d);
        return d;
    }
    else{
       Console.WriteLine("The input string was not in correct format");
   }
   return null;
}

The advantage of the TryParse method over the Parse method is that in case the input is not in correct format, it does not throw any exception and rather it returns a boolean indicating whether the value has been successfully parsed or not.

edited Jan 03 '19 at 10:15

answered Jan 03 '19 at 10:09

Transcendent

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The OPs problem is not that the string cannot be parsed. Thus your solution won´t help him/her at all. – MakePeaceGreatAgain Jan 03 '19 at 10:12
@HimBromBeere: Although I don't really agree with you, I improved my answer. – Transcendent Jan 03 '19 at 10:15

score 0 · Answer 2 · answered Jan 03 '19 at 10:09

0

Use Double.Parse:

private static double InputDouble(double prompt)
{
    Console.WriteLine("{0:s}: ", prompt);
    return Double.Parse(Console.ReadLine());
}

answered Jan 03 '19 at 10:09

Nick

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How do I convert a string to double using input?

2 Answers2