Formatting numbers

Formatting numbers

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:

1
double c = 10.25693;
2
Print("No formatting: " + c.ToString());
3
Print("Currency formatting: " + c.ToString("C"));
4
Print("Exponential formatting: " + c.ToString("E"));
5
Print("Fixed-point formatting: " + c.ToString("F2"));
6
Print("General formatting: " + c.ToString("G"));
7
Print("Percent formatting: " + c.ToString("P0"));
8
Print("Formatted to 2 decimal places: " + c.ToString("N2"));
9
Print("Formatted to 3 decimal places: " + c.ToString("N3"));
10
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:

1
double phoneNumber = 9165551022;
2
Print("Phone number: " + phoneNumber.ToString("(###) ### - ####"));

Corresponding output:

• Phone number
• Phone number: (916) 555 - 1022

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