How Can I Precisely Display Decimals in String Formatting?

Precisely display decimals using string formatting

In programming, it is often necessary to display values ​​in a specific format. String formatting provides a way to control how numbers are displayed, including the number of decimal places displayed.

For example, consider a price field that displays an integer or up to two decimal places. To do this, we need to adjust the format string based on whether the price contains decimals.

The following example illustrates the default formatting behavior:

<code>// 显示两位小数
String.Format("{0:0.00}", 123.4567); // "123.46"
String.Format("{0:0.00}", 123.4); // "123.40"
String.Format("{0:0.00}", 123.0); // "123.00"</code>

However, to display integers without decimals, we need to specify the number of mandatory and optional digits. For example, the following format string will display prices to up to two decimal places, or as an integer if the price has no decimal places:

<code>String.Format("{0:0.##}", 123.4567); // "123.46"
String.Format("{0:0.##}", 123.4); // "123.4"
String.Format("{0:0.##}", 123.0); // "123"</code>

In the above format string, "0" represents a mandatory number and "#" represents an optional number. Therefore, the string "0.##" ensures that the price has at least one digit before the decimal point and at most two digits after the decimal point.

To simplify the solution, we can use the ternary operator to check if the price is an integer and format it accordingly:

<code>var number = 123.46;
number.ToString(number % 1 == 0 ? "0" : "0.00");</code>

This method checks if the remainder of the price divided by 1 is zero, meaning an integer. If so, format the number as an integer ("0"), otherwise, format it with two decimal places ("0.00").

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