Inquiry about data type

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Hi, I have a variable which is in data type LONG. Is there any possibility the value being passed will turn in null value such as ""?

Below are my codes,

C#

private long UnitHeaderId;

if(UnitHeaderId != 0)
{
   //do something here
}
else
{
   //do something here
}

If the UnitHeaderId is null or empty(although with very low possibility that it would happen), will the IF statement still get executed or would it straight execute the ELSE statement? Thank you.

Posted 17-Mar-15 0:02am

Jamie888

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Tomas Takac 17-Mar-15 6:11am

Long value cannot be null or empty. Are you parsing the number from a string?

3 solutions

Solution 1

The variable "UnitHeaderId" you declared can never be null.
It's default value is 0.

If you want to have a nullable variable you must declare it like this:

C#

long? UnitHeaderId;

The question mark indicates that the variable is nullable.
More information about nullable types can be found here:
https://msdn.microsoft.com/en-us/library/1t3y8s4s.aspx[^]

Posted 17-Mar-15 0:11am

TheRealSteveJudge

Solution 2

Primitives types (like long, int, short, and their unsigned counterparts ulong, int, ushort, etc.) cannot be null, by design.

So, in your code, the only way for the else part to be reached would be when UnitHeaderId equals zero. UnitHeaderId will never be null. The only way to handle null values for primitive types is to use them with Nullable<T> type. This way:

C#

Nullable<long> nullableUnitHeaderId;
// OR
long? nullableUnitHeaderId;
</long>

Posted 17-Mar-15 0:13am

phil.o

v2

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CHill60 · Accepted Answer · 2015-03-17T00:13:00

This is something you can quite easily find out for yourself...

Try the code as it stands ... it won't compile -

Quote:
Use of unassigned local variable 'UnitHeaderId'

So try changing it to

long UnitHeaderId = null;

It still won't compile

Quote:
Cannot convert null to 'long' because it is a non-nullable value type

Now try faking a means of getting null into the variable at run-time... this will compile

C#

long UnitHeaderId;
long? x = null;
UnitHeaderId = (long)x;

if(UnitHeaderId != 0)

but as soon as you run it you get the runtime exception

Quote:
Nullable object must have a value.

So to answer your question, neither the IF nor the OR clause will be executed - if you somehow manage to get a null into UnitHeaderId you will get an exception thrown