Why can't int.TryParse parse number grouping (but double.TryParse can)?

Question

In C#, why can't int.TryParse parse number grouping (but double.TryParse can)?

        int i1 = 13579;
        string si1 = i1.ToString("N0");  //becomes 13,579
        int i2 = 0;
        bool result1 = int.TryParse(si1, out i2); //gets false and 0

        double d1 = 24680.0;
        string sd1 = d1.ToString("N0"); //becomes 24,680
        double d2 = 0;
        bool result2 = double.TryParse(sd1, out d2); //gets true and 24680.0

???

Answer 1

You have to specify the allowed NumberStyles, which is taken into account when parsing the string back into a number.

Determines the styles permitted in numeric string arguments that are passed to the Parse and TryParse methods of the integral and floating-point numeric types.

This returns true and stores the expected number in i2:

bool result1 = int.TryParse(si1,
   NumberStyles.AllowThousands, CultureInfo.CurrentCulture.NumberFormat, out i2);

You may also want to take a look at the other NumberStyles options. For example, NumberStyles.Number allows thousands as well as decimal points, white space, etc.

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The default value for int.TryParse (if none is specified) is NumberStyles.Integer, which allows only a leading sign, and leading and trailing white space.

The default for double.TryParse is NumberStyles.Float| NumberStyles.AllowThousands, which allows leading sign and white space, but also thousands, exponents and decimal points.