How to check the float decimal point is not longer than 0.00001? C#

Question

I am trying to limit the user input a number within 5 decimal points(e.g. 0.00007, 1.23456), if user input more than 5 decimal points, it will show a error message. How can I check it that is it longer than 5 dc? Thanks

public boolean isDc(float userInput)
{
    if(/** if userinput is within 5 dc**/)
         return true;
    else
         MessageBox.show("You should input within 5dc(E.g. 0.00001, 1.12345)");

    return false;
}

You can convert it to string then split on '.' and check its length. — Jasen, Dec 14 '16 at 02:59
A user input is a string. So you test the string and then convert to a float. — jdweng, Dec 14 '16 at 02:59
Closely related to [this](http://stackoverflow.com/a/9387756/643104) — Mahesh, Dec 14 '16 at 03:00
If you are using c# and you care about the precison of the decimal point then I suggest using `decimal` instead of `float`. — juharr, Dec 14 '16 at 03:03
@timleathart LOL, I forgot `Function` should change `public\private`. — Capslock10, Dec 14 '16 at 03:09
If you must use `float` code will be very awkward and result in accepting only small subset of values (as only fraction of `float` numbers can be represented with exactly 5 digits after the decimal point)... If `decimal` is ok than suggested duplicate covers it. — Alexei Levenkov, Dec 14 '16 at 03:12
So "0.12345" is acceptable input, but "0.123450" is excessively precise? If so, you need to inspect the user input, not a converted value as is done in the accepted answer. — HABO, Dec 14 '16 at 04:19

score 2 · Answer 1 · edited May 23 '17 at 11:53

This might do the trick for you but the userInput should be decimal

if(BitConverter.GetBytes(decimal.GetBits(userInput)[3])[2] == 5)
{
   //Show the error message
}

This will only check that if you have 5 decimal places or not. You can have a look at Find number of decimal places in decimal value regardless of culture and thus

First way could be

public boolean isDc(decimal userInput)
{
    if(BitConverter.GetBytes(decimal.GetBits(userInput)[3])[2] == 5)
         return true;
    else
         MessageBox.show("You should input within 5dc(E.g. 0.00001, 1.12345)");

    return false;
}

or

public boolean isDc(float userInput)
{
    decimal outdc;
    if(decimal.TryParse(userInput.ToString(), out outdc))
    {
        if(BitConverter.GetBytes(decimal.GetBits(outdc)[3])[2] == 5)
             return true;
        else
             MessageBox.show("You should input within 5dc(E.g. 0.00001, 1.12345)");
    }
    return false;
}

Closely related to [this](http://stackoverflow.com/questions/13477689/find-number-of-decimal-places-in-decimal-value-regardless-of-culture) right? — sujith karivelil, Dec 14 '16 at 03:09

Sajeetharan · Accepted Answer · 2016-12-14T03:11:09.927

1

 private Boolean isDc(string userInput)
        {
            var num = Decimal.Parse(userInput); //Use tryParse here for safety
            if (decimal.Round(num, 5) == num)            
                return true;
            else
                MessageBox.Show("You should input within 5dc(E.g. 0.00001, 1.12345)");

            return false;
        }

edited Dec 14 '16 at 03:11

answered Dec 14 '16 at 03:03

Sajeetharan

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I think you meant `decimal.Round(num, 5)` – juharr Dec 14 '16 at 03:05
@juharr corrected – Sajeetharan Dec 14 '16 at 03:11
Thank, I added `TryParse` for safety. It work. – Capslock10 Dec 14 '16 at 03:18

How to check the float decimal point is not longer than 0.00001? C#

2 Answers2