Default 0 to null in C#

Question

1.00/5 (2 votes)

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Hi All,

I tried the following to null the default 0, but no result. What is wrong in it.

datatype double.

C#

if (exg.CertficateNo == 0)
{
(exg.CertficateNo) = null;
}

Thanks in advance.

Posted 3-Jul-14 20:56pm

Murugan.NM

Updated 3-Jul-14 20:59pm

CPallini

v2

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Comments

Sergey Alexandrovich Kryukov 4-Jul-14 3:33am

Why? I understand why nullify anything on, for example, initialization, but why doing it on condition? Totally wrong idea.
—SA

5 solutions

Solution 1

you can't assign null to double, use nullable double

C#

double? CertficateNo;

then you can set

C#

CertficateNo =null;

read
Nullable Types (C# Programming Guide)[^]
Using Nullable Types (C# Programming Guide)[^]

Posted 3-Jul-14 20:59pm

DamithSL

Updated 3-Jul-14 21:01pm

v2

Comments

Sergey Alexandrovich Kryukov 4-Jul-14 3:21am

This is correct, a 5, but for floating-point types, there is a special, generally better, option.
Please see my answer.
—SA

Solution 2

You may assign null only to nullable data types[^] (as well to reference data types, of course).

Posted 3-Jul-14 21:01pm

CPallini

Comments

Sergey Alexandrovich Kryukov 4-Jul-14 3:22am

This is correct, a 5, but for floating-point types, there is a special, generally better, option.
Please see my answer.
—SA

Solution 4

use null able datatype while defining the "CertificateNo" property .
i.e. public double? CertificateNo { get; set; }

Posted 3-Jul-14 21:10pm

Pravuprasad

Comments

Murugan.NM 4-Jul-14 3:21am

I need to use formula with this field. if i declare nullable CertificateNo, then how to make formulas.

Sergey Alexandrovich Kryukov 4-Jul-14 3:22am

This is correct, a 5, but for floating-point types, there is a special, generally better, option.
Please see my answer.
—SA

Solution 5

All the solutions 1 to 4 are correct, but for floating-point types their is one more option which is important to know: NaN (not a number). You can use double.NaN and check as double.IsNaN:
http://msdn.microsoft.com/en-us/library/system.double.aspx[^].

This is the most economic and simple variant for "no data" value; it has many other uses. For further detail, please see:
http://en.wikipedia.org/wiki/Not_a_number[^],
http://en.wikipedia.org/wiki/IEEE_floating_point[^],
http://en.wikipedia.org/wiki/Floating_point[^].

—SA

Posted 3-Jul-14 21:21pm

Sergey Alexandrovich Kryukov

Comments

Rahul VB 4-Jul-14 5:17am

Yes sir. My 5

Andreas Gieriet 4-Jul-14 6:12am

Hello Sergey,
I agree that the question looks a bit odd.
When it comes to a meta state to tell if a value is given or not, then you have the choice to make the value nullable or to take an arbitrary value from the value range that is never used for that particular field.
For numeric values, you normally go for positive/negative, not zero/zero, min- or max-values, etc. or NaN, +Inf, -Inf.
The important task: whenever you select some value as a sentry, make sure your application can never produce it in any way in the normal mode of operation. For NaN, this can be the result of having NaN as input "value" in a calculation and if dynamically you calculate 0.0/0.0, etc.
Cheers
Andi

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sankarsan parida · Accepted Answer · 2014-07-03T21:03:00

Solution 3

Yes for this you have to use nullable double type in c#

double?

and in Entity database model

public System.Nullable<double> CertficateNo{ get; set; }

Posted 3-Jul-14 21:03pm

sankarsan parida

v2

Comments

Sergey Alexandrovich Kryukov 4-Jul-14 3:22am

This is correct, a 5, but for floating-point types, there is a special, generally better, option.
Please see my answer.
—SA