Weird Error for using ? Operator

Question

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The type of the conditional expression can not be determined?

I currently wrote this statement:

byte? Col_8 = (Rad_8.SelectedValue == null) ? null : byte.Parse(Rad_8.SelectedValue);

but it has this Error:

Type of conditional expression cannot be determined because there is no implicit conversion between '<null>' and 'byte'

why I can use null after ? ? what if equivalent of above code without if statement?

what is Rad_8.SelectedValue type? – CharlesB Jan 09 '12 at 11:55 — CharlesB, Jan 09 '12 at 11:55

score 8 · Accepted Answer · answered Jan 09 '12 at 11:55

8

The compiler cannot infer the type of the conditional statement because null has no type and it does not consider the expected return value. Use

(Rad_8.SelectedValue == null) ? (byte?)null : byte.Parse(Rad_8.SelectedValue);

answered Jan 09 '12 at 11:55

Jens

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score 0 · Answer 2 · answered Jan 09 '12 at 11:54

0

if(Rad_8.SelectedValue == null)
    Col_8 = null;
else 
    Col_8 = byte.Parse(Rad_8.SelectedValue);

answered Jan 09 '12 at 11:54

Haris Hasan

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score 0 · Answer 3 · answered Jan 09 '12 at 11:56

I believe it is because the method byte.Parse(...) does not return a nullable type, therefore the compiler is saying there is not implicit conversion between the null- and byte-types. Try casting the null value with (byte?) to explicitly specify it's type.

Weird Error for using ? Operator

3 Answers3