CODEWITHSUNDEEP
c#.netdecimalint
Yaakov Ellis
Yaakov Ellis

Reputation: 41490

Best way to get whole number part of a Decimal number

What is the best way to return the whole number part of a decimal (in c#)? (This has to work for very large numbers that may not fit into an int). 

GetIntPart(343564564.4342) >> 343564564
GetIntPart(-323489.32) >> -323489
GetIntPart(324) >> 324

The purpose of this is: I am inserting into a decimal (30,4) field in the db, and want to ensure that I do not try to insert a number than is too long for the field. Determining the length of the whole number part of the decimal is part of this operation.

Upvotes: 106

Views: 218263

Answers (8)

Rusty Nail
Rusty Nail

Reputation: 2710

Forgetting the meaning of the term: "Whole Number" seems common in the answers, and in the Question.

Getting the whole number from the number: 4 is simple:

1 x 4 = 4 <- A Whole Number! The first Whole Number!
2 x 4 = 8 <- A Whole Number!
3 x 4 = 12 <- A Whole Number!

Rounding a Number, to get a Whole Number is a cheats method of getting the Whole Numbers! Rounding it removing the Non-Whole Number part of the Number!

1.3 x 4 = 5.2 <- NOT a Whole Number!
1 x 343564564.4342 <- NOT a Whole Number!

Its important to understand what a Whole Number is!

4 / 1 = 4 <- A Whole Number!
4 / 2 = 2 <- A Whole Number!
4 / 3 = 1.333 recurring  <- NOT A Whole Number!

Please ask, and answer the questions with a bit more Accuracy Peeps...

double A = Math.Abs(343564564.4342);
double B = Math.Floor(343564564.4342);
double C = Math.Ceiling(343564564.4342);
double D = Math.Truncate(343564564.4342);

Returns:

A = 343564564.4342
B = 343564564
C = 343564565
D = 343564564

or:

double E = Math.Round(343564564.4342, 0);
E = 343564564

Is a Mathematical Function, thus changing the Number, and not working with Whole Numbers. Your Rounding Non-Whole Numbers!

Upvotes: -1

luka
luka

Reputation: 637

I hope help you.

/// <summary>
/// Get the integer part of any decimal number passed trough a string 
/// </summary>
/// <param name="decimalNumber">String passed</param>
/// <returns>teh integer part , 0 in case of error</returns>
private int GetIntPart(String decimalNumber)
{
    if(!Decimal.TryParse(decimalNumber, NumberStyles.Any , new CultureInfo("en-US"), out decimal dn))
    {
        MessageBox.Show("String " + decimalNumber + " is not in corret format", "GetIntPart", MessageBoxButtons.OK, MessageBoxIcon.Error);
        return default(int);
    } 

    return Convert.ToInt32(Decimal.Truncate(dn));
}

Upvotes: 1

Mattheu Norwood
Mattheu Norwood

Reputation: 50

   Public Function getWholeNumber(number As Decimal) As Integer
    Dim round = Math.Round(number, 0)
    If round > number Then
        Return round - 1
    Else
        Return round
    End If
End Function

Upvotes: 0

Amit Gohel
Amit Gohel

Reputation: 11

Very easy way to separate value and its fractional part value.

double  d = 3.5;
int i = (int)d;
string s = d.ToString();
s = s.Replace(i + ".", "");

s is fractional part = 5 and
i is value as integer = 3

Upvotes: 0

user1228
user1228

Reputation:

By the way guys, (int)Decimal.MaxValue will overflow. You can't get the "int" part of a decimal because the decimal is too friggen big to put in the int box. Just checked... its even too big for a long (Int64).

If you want the bit of a Decimal value to the LEFT of the dot, you need to do this:

Math.Truncate(number)

and return the value as... A DECIMAL or a DOUBLE.

edit: Truncate is definitely the correct function!

Upvotes: 247

Mark Carpenter
Mark Carpenter

Reputation: 17775

I think System.Math.Truncate is what you're looking for.

Upvotes: 28

Keith
Keith

Reputation: 155652

Depends on what you're doing.

For instance:

//bankers' rounding - midpoint goes to nearest even
GetIntPart(2.5) >> 2
GetIntPart(5.5) >> 6
GetIntPart(-6.5) >> -6

or 

//arithmetic rounding - midpoint goes away from zero
GetIntPart(2.5) >> 3
GetIntPart(5.5) >> 6
GetIntPart(-6.5) >> -7

The default is always the former, which can be a surprise but makes very good sense.

Your explicit cast will do:

int intPart = (int)343564564.5
// intPart will be 343564564

int intPart = (int)343564565.5
// intPart will be 343564566

From the way you've worded the question it sounds like this isn't what you want - you want to floor it every time.

I would do:

Math.Floor(Math.Abs(number));

Also check the size of your decimal - they can be quite big, so you may need to use a long.

Upvotes: 5

Noldorin
Noldorin

Reputation: 147260

You just need to cast it, as such:

int intPart = (int)343564564.4342

If you still want to use it as a decimal in later calculations, then Math.Truncate (or possibly Math.Floor if you want a certain behaviour for negative numbers) is the function you want.

Upvotes: 0

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