Ran into an interesting problem today.

I need to truncate a number to 2 decimal places, which basically means chopping off the extra digits.

Eg:

2.919 -> 2.91

2.91111 -> 2.91


Why? This is what SQL server is doing when storing a number of a particular precision. Eg, if a column is Decimal(8,2), (TxnComponent.AdjustedCost), and you try to insert/update a number of 9.1234, the 3 and 4 will be chopped off.

I need to do it in c# code to mimick what the database is doing.

As far as I can work out there's no library available to do it!

The only possible ways of doing it are either:


1. Using the stringformatter to "print" it out only two decimal places, and then casting it to a decimal,

eg:

decimal longDecimal = 2.1345

decimal shorterDecimal = Convert.ToDecimal(longDecimal.ToString("0.##"));

// shorterDecimal is now 2.13

I'm not happy with this because it involves a to-string and then another string to decimal conversion. Ridiculous!


2. Using Math.Truncate (which only accepts an integer), so I can multiply it by 100, truncate it, then divide by 100. eg:

decimal longDecimal = 2.1235;

decimal shortDecimal = Math.Truncate(longDecimal * 100) / 100;

I'm also not happy with this because if longDecimal is 0, I'll get a divide by 0 error. Ridiculous.



Surely there's a better + easier way!! Any suggestions?

Direct Link Tags: truncating decimal points in c#

Date: Thursday, October 01, 2009 15:16
User: Levi
Comment:
decimal shortDecimal = Math.Truncate(0 * 100) / 100;

I fail to see the divide by zero?

Date: Thursday, October 01, 2009 21:13
User: lach
Comment: Yeah I know. I realised that. I'm a git. It's still a bodgy solution, but I guess it works.