Linq data type comparison with Double

Question

In my Linq query I have a where statement that looks like this

&& vio.Bows.Any(nw => nw.XCoordinate.Equals(currVio.XCoordinate)))

values are

nw.XCoordinate = 4056.48751252685
currVio.XCoordinate = 4056.488

Thus the statement of Equals is not working, what is the easiest way to round?

public double XCoordinate { get; set; }

You could not simply use Equals to compare two double number. Check this question: http://stackoverflow.com/questions/1398753/comparing-double-values-in-c-sharp — 2power10, May 23 '13 at 01:53

score 3 · Accepted Answer · answered May 23 '13 at 01:52

3

You can use the usual way of comparing double for proximity by calculating the absolute difference, and comparing it to a small value:

Math.Abs(x - y) < 1E-8 // 1E-8 is 0.00000001

For example, you can use this approach in a LINQ query like this:

&& vio.Bows.Any(nw => Math.Abs(nw.XCoordinate-currVio.XCoordinate) < 0.001)

answered May 23 '13 at 01:52

Sergey Kalinichenko

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Just noticed that sometimes the number could be 4056.49 – May 23 '13 at 03:06
@ChrisHamilton Then you need to increase the "tolerance" level to something greater than `0.001`, say, `0.005`. – Sergey Kalinichenko May 23 '13 at 03:24
I understand, I was trying 0.01 which worked but 0.005 works so much better! thx again – May 23 '13 at 04:18

score 0 · Answer 2 · answered May 23 '13 at 02:14

You could also use Math.Round i.e.:

double x = 4056.48751252685;
var newx = Math.Round(x,3);

So if you knew you always wanted 3 decimal places you could:

&& vio.Bows.Any(nw => Math.Round(nw.XCoordinate,3).Equals(math.Round(currVio.XCoordinate,3))))

You could go further and implement IEquetable, and override the equals function, determine which of the two values has the least number of decimal places, round both to that value and compare.

Linq data type comparison with Double

2 Answers2