C# String.Format to One Decimal Place

Question

I'm trying to format a toString to one decimal place but it keeps going to something like 21.0445445454. Here's the line of code please let me know what I'm doing wrong

 double heightInchToFoot = (12 * Convert.ToDouble(heightFtBox.Text)) +Convert.ToDouble(heightInchBox.Text);
        double bmi = (Convert.ToDouble(weightBox.Text) * 703) / (heightInchToFoot * heightInchToFoot);
        bmiDisplay.Text = String.Format("{0:0.0}", bmi.ToString());//This is the line of code I'm referring to

I don't know if I'm right but have you tried ############.# format?? — c_str
– c_str, Commented Jul 13, 2014 at 2:13

user2864740 · Accepted Answer · 2014-07-13 02:20:04Z

5

The problem is the use of bmi.ToString() which converts the double to a string using the default Double.ToString format/rules¹. Because of that, the actual Format deals with a string (which doesn't understand decimal formatting) and not the actual double value.

Instead, it should be

String.Format("{0:0.0}", bmi)

or

bmi.ToString("0.0")

¹ From the documentation:

The Double.ToString() method formats a Double value in the default ("G", or general) format of the current culture.

edited Jul 13, 2014 at 2:20

answered Jul 13, 2014 at 2:14

user2864740

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