Custom numeric format string to always display the sign

Question

Is there any way I can specify a standard or custom numeric format string to always output the sign, be it +ve or -ve (although what it should do for zero, I'm not sure!)

Solution 1

Yes, you can. There is conditional formatting. See Conditional formatting in MSDN

eg:

string MyString = number.ToString("+0;-#");

Where each section separated by a semicolon represents positive and negative numbers

or:

string MyString = number.ToString("+#;-#;0");

if you don't want the zero to have a plus sign.

Solution 2

Beware, when using conditional formatting the negative value doesn't automatically get a sign. You need to do

string MyString = number.ToString("+#;-#;0");

Solution 3

You can also use format strings in string.Format(); the format string is separated from the index with a colon (':')

var f = string.Format("{0}, Force sign {0:+#;-#;+0}, No sign for zero {0:+#;-#;0}", number);

For number { +1, -1, 0 } this gives:

1, Force sign +1, No sign for zero +1
-1, Force sign -1, No sign for zero -1
0, Force sign +0, No sign for zero 0

You can also use an interpolated string instead of string.Format to obtain the same result:

var f = $"{number}, Force sign {number:+#;-#;+0}, No sign for zero {number:+#;-#;0}";

Solution 4

Contrary to the other answers it seems that if you want to get +1, -1, +0 (for arguments 1, -1, 0) you need to use the format:

String.Format("{0:+#;-#;+0}", 0));  // output: +0

or

String.Format("{0:+0;-#}", 0));  // output: +0

If you use just +#;-# it will display just + (not +0) for 0.

The "#" Custom Specifier (at https://msdn.microsoft.com/en-us/library/0c899ak8.aspx)

Note that this specifier never displays a zero that is not a significant digit, even if zero is the only digit in the string. It will display zero only if it is a significant digit in the number that is being displayed.

Also please keep in mind that if you need any decimal precision you need to specify it like that:

String.Format("{0:+0.##;-#.##}", 0));  // output: +0

or, if you wan't zeros to always show up, like that:

String.Format("{0:+0.00;-#.00}", 0));  // output: +0.00

Solution 5

For a numeric expression of any type:

+###,###,###,###,###,###,###,###,###,##0.###,###,###,###,###,###,###,###,###,###;-###,###,###,###,###,###,###,###,###,##0.###,###,###,###,###,###,###,###,###,###;0

Use three parts for three cases: positive;negative;zero

Other aspects of the example:

• Zero is not signed. You could have it show as anything, such as "zero".

• Absolute values less than one have a leading 0 before the decimal point. Adjust to taste.

• Number of digits is for the largest and smallest absolute decimal values. Adjust to taste.

• Decimal point character is culture-specific. .NET substitutes.

• Grouping separators are optional. The character is culture-specific. .NET substitutes. (The positions are also culture-specific but that's only controlled by your format string.) You also use any other character except the special characters for Format (which include , . # 0).

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Comments

[Roman Starkov]

Fixed a bug whereby negatives did not get a minus.

[rbaleksandar]

Thanks you so much! I have been busting my head for like an hour to figure out what's the equivalent of the '+'-flag of printf in C# and you gave me THE answer.

[orion elenzil]

with +#;-#, for the value 0 I get just "+", with no actual 0. for me I want 0 to appear as "+0", so this works: +#;-#;+0.

[Shahab]

Thanks! Mixing this with '' will do great things! Look at this: Changes.ToString("'('#' ▲)';'('#' ▼)';''") ! It saved me lots of time and hundreds of if statements! :)

[Kamil Szot]

Last line of your answer should say "Default format 0, Force sign +, No sign for zero 0." because that's the actual result of +#;-# format for value 0

[Kamil Szot]

@orionelenzil I had the same problem. You could also do +0;-# instead of +#;-#;+0 This answer was really misleading for me.

[Edward]

Thank you, Kamil - I missed that. I have now corrected the force sign format: +#;-#;+0 (instead of +#;-#)

[Andrew]

As others pointed out, +0;-# gives you the same result with cleaner code.

[Andrew]

You can get the force sign behavior with a simpler format: +0;-#. :)

[Edward]

@Andrew, Indeed, but I prefer +#;-#;+0 over +#;-# as this makes it clearer that 0 will be formatted as +0

[Glenn Slayden]

@Shahab I like it. Note that you don't even have to display the numeric value of the number with the controlling sign if you don't want to... string msg = $"The stock market is {delta:▲;▼;~} today.";.

[navigator]

A format of #,##0 is sufficient for any number of thousands separators.