Rounding function to nearest 1/4

Question

We only want to auto round the user entered values to the nearest .25 hour interval. So the user can enter 1.55 and it would round to 1.50 when saving to the database. If the user enters 1.90 to would save 2.00 to the database.

Answer 1

You can use Math.Round with MidpointRounding.AwayFromZero like;

double d = 1.55 * 4;
double i = Math.Round(d, MidpointRounding.AwayFromZero);
Console.WriteLine(i / 4);

Output will be

1.5

Here a demonstration.

As an explanation, multiplying 4 and then rounding gives you exactly 4 times with your decimal part like .00, .25, .50, .75.

Than dividing this double to 4, gives you exactly nearest .25 hour interval.

Here a full codes of examples;

double[] array = new[] { 1.0, 1.1, 1.2, 1.25, 1.3, 1.4, 1.5, 1.55, 1.6, 1.7, 1.75, 1.8, 1.9 };
foreach (double item in array)
{
    double d = item * 4;
    double i = Math.Round(d, MidpointRounding.AwayFromZero);
    Console.WriteLine(i / 4);
}

Output will be;

1.0 gives you 1.0
1.1 gives you 1.0
1.2 gives you 1.25
1.25 gives you 1.25
1.3 gives you 1.25
1.4 gives you 1.5
1.5 gives you 1.5
1.55 gives you 1.5
1.6 gives you 1.5
1.7 gives you 1.75
1.75 gives you 1.75
1.8 gives you 1.75
1.9 gives you 2.0

Here a full demonstration.