从double转换为decimal

Question

I am developing a weather application in C# using the Google weather XML file and I am having trouble using calculations in a class file. I am trying to convert farenheit to celcius with the folliowing method:

public static class Helper
{
    public static decimal CalculateTemp(decimal input)
    {
     return Math.Round((input - 32) * 5 / 9 / 1.0) * 1.0 + "°C";
    }
}

"input" is where the weather data is called such as the highest temp. of today. I am getting the following errors upon compiling:

Error 23: The best overloaded method match for 'Weather.Helper.CalculateTemp(decimal)' has some invalid arguments

Error 24: Argument 1: cannot convert from 'double' to 'decimal'

Error 25 : Operator '/' cannot be applied to operands of type 'decimal' and 'double'

I am not sure how to fix this..

Answer 1

Don't use decimal for a temperature, double is enough.

Also, don't return "°C" cause it's a number, not a string:

public static double CalculateTemp(double input)
{
    return Math.Round((input - 32) * 5 / 9);
}

Answer 2

1.0 is a double , not a decimal . Use the suffix m or M to mark a number as a decimal .
("M" stands for "Money", as this type is normally used for financial transactions.)

(input - 32) * 5M / 9M

and you won't even need the * 1.0

Answer 3

if you want to use the decimal (rather than double), you'd have to refactor as:

public static class Helper
{
    public static string CalculateTemp(decimal input)
    {
        return Math.Round(((input - 32) * 5 / 9 / 1.0m)) + "°C";
    }
}

or:

public static class Helper
{
    public static string CalculateTemp(decimal input)
    {
        return Math.Round(((input - 32) * 5 / 9 / (decimal)1.0)) + "°C";
    }
}

notice also that you have to change the method signature to return a string due to the "°C" at the end.