How can I return a 0 from a function that parses a string to find an int if it finds a number with a decimal point?

Question

I have this code:

public int GetIntSetting(Settings setting, int nullState)
{
    var s = GetStringSetting(setting);
    if (string.IsNullOrEmpty(s))
        return nullState;
    return int.Parse(s);
}

If the value of s is something like 1.234 then the functions creates an exception.

How can I make it so that if the value of s has a decimal point then the function returns 0?

How would you differentiate between the user entered zero or just `1.234`? Throwing an exception on invalid user-input is okay. — MakePeaceGreatAgain, Jul 31 '17 at 11:42
not an expert of c# but you can probably parse it to a decimal/float type and check it is the same value than the int one. — ValLeNain, Jul 31 '17 at 11:42
Please read [ask] and try searching before asking a new question. — CodeCaster, Aug 01 '17 at 12:12

score 4 · Accepted Answer · edited Sep 29 '17 at 10:28

4

Use TryParse:

int parsed;
var result = int.TryParse(data, out parsed) ? parsed : 0;

Or if using C#7.0 with the out var declaration:

var result = int.TryParse(data, int out parsed) ? parsed : 0;

Note that as HimBromBeere commented you will not know when it is 0 because it is not a valid int or because the input is actually the input.

All together:

public int GetIntSetting(Settings setting, int nullState)
{
    var s = GetStringSetting(setting);
    if (string.IsNullOrEmpty(s))
        return nullState;
    return int.TryParse(s, out int parsed) ? parsed : 0;
}

edited Sep 29 '17 at 10:28

Graham

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answered Jul 31 '17 at 11:44

Gilad Green

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It should be `int.TryParse(data, out int result)`? – Siva Gopal Jul 31 '17 at 11:50
@SivaGopal - yap, my mistake. Corrected – Gilad Green Jul 31 '17 at 11:52
Actually I just realized. I only need to check the string for the existence of a "." I think that would be maybe more clean. – Alan2 Jul 31 '17 at 11:54
@Alan - that depends - do you know 100% that the string will not have letters in it? It is just safer to use `TryParse` when parsing to int, instead of getting an exception.. (unless that's the desired response) – Gilad Green Jul 31 '17 at 11:56
@Alan - especially with C#7.0 it is nice and inline to check it – Gilad Green Jul 31 '17 at 11:56
Do you mean to have s instead of data ? – Alan2 Jul 31 '17 at 13:25
@Alan - yes. ops :) correcting now – Gilad Green Jul 31 '17 at 17:19

score 2 · Answer 2 · answered Jul 31 '17 at 11:44

2

int.TryParse will return false for decimal numbers. This is a bit broader than your question of jiust handling decimal points, but is probably a sensible thing to do anyway:

int x = 0;
Console.WriteLine(int.TryParse("1.234",out x)); // outputs False

So you could change your code to

public int GetIntSetting(Settings setting, int nullState)
{
    var s = GetStringSetting(setting);
    if (string.IsNullOrEmpty(s) )
        return nullState;
    var result = 0;
    if(!int.TryParse(s,out result))
        return 0;
    return result;
}

answered Jul 31 '17 at 11:44

Jamiec

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Actually I just realized. I only need to check the string for the existence of a "." I think that would be maybe more clean. – Alan2 Jul 31 '17 at 11:54
3

So a setting for `abc123$%$£!%"&` is an acceptable `int` to you? – Jamiec Jul 31 '17 at 11:55
@Alan If you have another solution to your problem feel free to post an answer yourself. However in this particular case I won´t recommend that because of the previously mentioned comment from Jamiec. – MakePeaceGreatAgain Jul 31 '17 at 12:01

score 1 · Answer 3 · answered Jul 31 '17 at 11:50

1

I'd propose TryParse testing if it would parse as an int or a double:

double theNumber;
if (Int32.TryParse(s, out theNumber)) return (int)theNumber;
else if (Double.TryParse(s, theNumber)) return 0;

// Here is not an int or double, i.e. return nullState for example

answered Jul 31 '17 at 11:50

donquijote

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Actually I just realized. I only need to check the string for the existence of a "." I think that would be maybe more clean. – Alan2 Jul 31 '17 at 11:54

How can I return a 0 from a function that parses a string to find an int if it finds a number with a decimal point?

3 Answers3