C# Not Rounding Double

Question

When I pass this object back as JSON, it looks like this:

0.000000000000000e+000

My code in C# is:

// get adjustments for user
IEnumerable<Severity> existingSeverities = 
    from s in db.AdjusterPricingGrossLossSeverities
    where s.type == type
    && s.adjusterID == adj.id
    select new Severity
    {
        id = s.severity,
        adjustment = Math.Round((double)s.adjustment, 2, MidpointRounding.AwayFromZero).ToString(),
        isT_E = (bool)s.isTimeAndExpense
    };

How can I make it just round to two decimal places (0.00)?

Why? decimal places only matter when presenting to the user. — Henk Holterman, Jun 14 '13 at 13:23
It is rounding to 2 decimal places but it's still being stored as `double` which is by definition many more decimal places. You will need to present in JavaScript however you like as Henk says. — El Ronnoco, Jun 14 '13 at 13:25
@ElRonnoco I am storing it as a string (`adjustment` is a string whereas `s.adjustment` is the double) — user1477388, Jun 14 '13 at 13:29
@HenkHolterman I am passing it as a string, not a double. So, the presentation matters here. — user1477388, Jun 14 '13 at 13:30
@GrantWinney `s.adjustment` is a `?double` (optional double). `adjustment`, however, is `string`. — user1477388, Jun 14 '13 at 13:30

score 3 · Answer 1 · edited May 23 '17 at 12:21

3

Use;

dec.ToString("#.##");

See this answer for more information

If it's a nullable double in a Console app do;

    double ? d = 2.22222;
    Console.WriteLine(d.Value.ToString("#.##"));

edited May 23 '17 at 12:21

Community

1
1

answered Jun 14 '13 at 13:24

Sam Leach

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Syntax error: `No overload method for 'ToString' takes 1 arguments`. Code: `adjustment = s.adjustment.ToString("#.##"),` – user1477388 Jun 14 '13 at 13:27
@user1477388 Then are you sure s.adjustment is a double? – Tory Jun 14 '13 at 13:30
@Tory it is a `?double` (hence the cast). – user1477388 Jun 14 '13 at 13:31
@GrantWinney Now, I get a LINQ to SQL error `Method 'System.String ToString(System.String)' has no supported translation to SQL.` But that's closer, at least. – user1477388 Jun 14 '13 at 13:35
If it's stored as a nullable double in the database, you'll have a bit of a job shoving a string in there I'd have thought. – Matthew Watson Jun 14 '13 at 13:38

score 1 · Answer 2 · answered Jun 14 '13 at 13:50

I think that you are confusing two things. The "real" number is not what you see. The real number is stored internally in a binary format. The decimal digits that you see do not exist in this internal format. What you see is the conversion of this value to a decimal representation as a string.

The conversion of any internal binary representation to a human visible string is called formatting. The Round function does not format. See this example:

double x = 0.123456000000000e+000;
double y = Math.Round(x, 2, MidpointRounding.AwayFromZero);
// y ====> 0.120000000000000e+000;

The rounding function changes the internal value. What you need is probably not to change the value but to display the unchanged value with only two digits:

string formattedValue = x.ToString("N2");

If you are deling with currencies, use decimal rather than double. decimal uses a binary encoded decimal format internally. Values like 1/10 cannot be represented precisely as binary number in a computer just like 1/7 cannot be represent precisely in decimal notation (0.142857142857...). But 1/10 has an exact internal representation when stored as a decimal.

Thank you, that makes sense. However, this wouldn't have worked as is (inline), ultimately, since LINQ to SQL works the way it does. The only solution that worked for me is the one I found and posted here http://stackoverflow.com/a/17109950/1477388 — user1477388, Jun 14 '13 at 13:53

Tory · Answer 3 · 2013-06-14T14:37:17.773

Try this:

// get adjustments for user
IEnumerable<Severity> existingSeverities = 
from s in db.AdjusterPricingGrossLossSeverities
where s.type == type
&& s.adjusterID == adj.id
select new Severity
{
    id = s.severity,
    adjustment = s.adjustment.GetValueOrDefault().ToString("0.##"),
    isT_E = (bool)s.isTimeAndExpense
 };

-Edit-

I think that maybe you will need to have the Severity class have a Property that takes a double and saves a string to Severity.adjustment, like so:

 Severity
 {
      //rest of class as normal

      public double SetAdjustment
           {
                set { adjustment = value.ToString("0.00"); } }
           }
 }

-Edit, part 2-

// get adjustments for user
IEnumerable<Severity> existingSeverities = 
from s in db.AdjusterPricingGrossLossSeverities
where s.type == type
&& s.adjusterID == adj.id
select new Severity
{
    id = s.severity,
    SetAdjustment = s.adjustment.GetValueOrDefault(),
    isT_E = (bool)s.isTimeAndExpense
 };

The rest of your code should not need to be changed, it should still use (Severity variable).adjustment as normal. This is just to get around the fact that there is not guaranteed way to translate .Net's Standard Numeric Format Strings into SQL's Convert, much less any custom formatting.

Thanks, but I get the error `Method 'System.String ToString(System.String)' has no supported translation to SQL.` — user1477388, Jun 14 '13 at 13:36
How do I use your method in the context of my LINQ to SQL query? — user1477388, Jun 14 '13 at 13:57

score 0 · Accepted Answer · answered Jun 14 '13 at 13:44

Turns out, this was a LINQ to SQL issue. I did this, and it works...

// get adjustments for user
IEnumerable<Severity> existingSeverities = 
    from s in db.AdjusterPricingGrossLossSeverities
    where s.type == type
    && s.adjusterID == adj.id
    select new Severity
    {
        id = s.severity,
        adjustment = roundtest(s.adjustment.GetValueOrDefault()),
        isT_E = (bool)s.isTimeAndExpense
    };

// test method...
public string roundtest(double num)
{
    return num.ToString("#.##");
}

C# Not Rounding Double

4 Answers4