Ternary operation with nullable int in C#

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Hey peps,

Is this statement incorrect..? If yes Why? Please specify some references to support your answers...

C#

int buzzInfluence = 0;
int.tryParse(Request.QueryString["buzzInfluence"], out buzzInfluence);

int? z = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? null : buzzinflunce;

Posted 9-Jan-13 0:31am

the headless nick

Updated 9-Jan-13 1:10am

v3

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Ibrahim Uylas 9-Jan-13 6:46am

What is the type of buzzinflunce? is it int ?

the headless nick 9-Jan-13 7:11am

updated my query, thanks :)

2 solutions

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Tharaka MTR · Accepted Answer · 2013-01-09T01:54:00

Solution 2

see the details error message you got
Type of conditional expression cannot be determined because there is no implicit conversion between '<null>' and 'int'

you can fix this issue by changing your code as follows

C#

int buzzInfluence = 0;
int.TryParse(Request.QueryString["buzzInfluence"], out buzzInfluence);
int? z = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? null : (int?)buzzInfluence;

int? zz = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? (int?)null : buzzInfluence;

you have to modify your code by adding (int?)buzzInfluence or (int?)null

also, here are some more alternatives

C#

int? zzz = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? default(int?) : buzzInfluence;

int? zzzz = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? new int?() : buzzInfluence;

Posted 9-Jan-13 1:54am

Tharaka MTR

Updated 9-Jan-13 6:40am

v3

Comments

phil.o 9-Jan-13 8:20am

int? zz = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? (int?)null : buzzInfluence;
won't work because the return type isn't the same for both possibilities

Tharaka MTR 9-Jan-13 12:19pm

I can't agree your comments. try this, this works definitely.

Tharaka MTR 9-Jan-13 12:38pm

I don't know who are the persons down voted my answer. I only know two person did that. But I'm pretty sure they haven't tested this or they haven't check the actual logic behind the solution. And also, I'm pretty sure they had some doubt with the following part

int? zz = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? (int?)null : buzzInfluence;

Logic behind here is, you can cast the null value to nullable type. Please googled and verified. or please try this in visual studio. even you can use as follows also

int? zzz = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? default(int?) : buzzInfluence;

int? zzzz = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? new int?() : buzzInfluence;

I'm just asking please check this and correct your voting.

Richard MacCutchan 9-Jan-13 18:05pm

I just tried your code and it worked. Unfortunately my 5 vote was not enough to counteract the three 1s. However, you really should not fret about this, as downvotes are largely irrelevant; your reputation will grow despite these little setbacks.

Tharaka MTR 9-Jan-13 21:47pm

Yep.. Thx Richard :)

Tharaka MTR 9-Jan-13 13:56pm

At least, if you can give me why you are down voting this? then I can provide the answers..

the headless nick 9-Jan-13 23:46pm

Good.. I got a decent explanation.. thanks guys..
Dont' worry I too voted 5. ;)

OriginalGriff · Accepted Answer · 2013-01-09T01:16:00

No - you need to cast the int to a nullable int:

C#

int buzzInfluence = 0;
int.TryParse(Request.QueryString["buzzInfluence"], out buzzInfluence);

int? z = string.IsNullOrWhiteSpace(Request.QueryString["buzzInfluence"]) ? null : (int?)buzzInfluence;

If you don't, you are returning two different types, and it won't allow that.
But personally, I would do the test first, and then do the TryParse only if it wasn't empty - or use the result of the TryParse itself...