Formatting numbers

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Formatting numbers

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String formatting on numbers is very useful for creating readable output. This can be done through the use of the number object's ToString() method.


A common practice is printing out mathematical operations with the use of the ToString() method on the double object. What usually happens is the printing of a long string containing all the decimal places existing in the double. This sometimes makes output cluttered and hard to read. Luckily, C# has a robust set of string formatting options available to make the string more comprehendible.


Here is a list of common formatting options available in the ToString() method:


double c = 10.25693;

Print("No formatting: " + c.ToString());

Print("Currency formatting: " + c.ToString("C"));

Print("Exponential formatting: " + c.ToString("E"));

Print("Fixed-point formatting: " + c.ToString("F2"));

Print("General formatting: " + c.ToString("G"));

Print("Percent formatting: " + c.ToString("P0"));

Print("Formatted to 2 decimal places: " + c.ToString("N2"));

Print("Formatted to 3 decimal places: " + c.ToString("N3"));

Print("Formatted to 4 decimal places: " + c.ToString("N4"));


The corresponding output is as follows:


No formatting: 10.25693

Currency formatting: $10.26

Exponential formatting: 1.025693E+001

Fixed-point formatting: 10.26

General formatting: 10.25693

Percent formatting: 1,026 %

Formatted to 2 decimal places: 10.26

Formatted to 3 decimal places: 10.257

Formatted to 4 decimal places: 10.2569


For custom formatting you can use the following:


double phoneNumber = 9162031022;

Print("Phone number: " + phoneNumber.ToString("(###) ### - ####"));


Corresponding output:


Phone number: (916) 203 - 1022



For more information on general string formatting this guide may be of use. Many other resources can be found online through a Google search as well.