CODEWITHSUNDEEP
c#.netrounding
isXander
isXander

Reputation: 137

How to round to any number in C#?

I am in the middle of making a calculator in C# and I want to round to nearest 1, 10, 100, etc and also like nearsest 0.1, 0.001, etc. I have seen other projects that tell me how to do it but I tried and they don't seem to work.

I've tried:

textBox1.Text = Convert.ToString(Math.Round(Convert.ToDouble(Label1.Text), Convert.ToInt32(textBox1.Text), MidpointRounding.AwayFromZero));

and...

textBox1.Text = Convert.ToString(Math.Round(Convert.ToDouble(Label1.Text), Convert.ToInt32(textBox1.Text)));

and...

textBox1.Text = Convert.ToString(Convert.ToInt32(Label1.Text) / Convert.ToInt32(textBox1.Text) * Convert.ToInt32(textBox1.Text));

Upvotes: 2

Views: 3093

Answers (2)

St. Pat
St. Pat

Reputation: 749

You can make an Extension method to do it, using the same idea from Jonathon's answer. You divide the input by the interval you choose, round it using Math.Round, and then multiply the rounded number by the interval.

static class Extensions
{
    public static int RoundToInterval(this int i, int interval)
    {
        if (interval == 0)
        {
            throw new ArgumentException("The specified interval cannot be 0.", nameof(interval));
        }
        return ((int)Math.Round((double)i / (double)interval)) * interval;
    }
}

Calling it will look like so.

int input = 13;
var result = input.RoundToInterval(10);

The result of the previous example call will be 10. Change input to 16, and the result will be 20. If you pass 100 as the argument to RoundToInterval, the result will be 0, and 51 (and 50 with the default MidpointRounding choice) will give the result of 100.

Upvotes: 1

Jonathon Chase
Jonathon Chase

Reputation: 9704

Math.Round has overloads that allow you to round to a particular decimal.

e.g.

Math.Round(0.05, 1, MidpointRounding.AwayFromZero);

will result in 0.1

If you want to round to the nearest 10, 100, etc, you will need to do a bit more math.

Math.Round((double)50 / 100, MidpointRounding.AwayFromZero) * 100;

results in 100, for rounding to the nearest hundred, while

Math.Round((double)55 / 10, MidpointRounding.AwayFromZero) * 10;

will get you to the nearest 10, in this case 60.

Upvotes: 5

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