[RESOLVED] Passing Nulls

[Bill Crawley]

Hi ALL,

I'm using VS2010 C# 4.0.

I have a method declared:

public spGetBorderauxLog(String Client, String ProcessDate, Int16? Status, Boolean? Actioned)

and am attempting to call with the following:

...spGetBorderauxLog(drpClient.Text, datepicker.Value == "" ? null : datepicker.Value, drpStatus.SelectedItem.Value == "" ? null : Convert.ToInt16(drpStatus.SelectedItem.Value), null);

I'm receiving the red line under the following text:

null : Convert.ToInt16(drpStatus.SelectedItem.Value)

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

I've declared the parameter as nullable, so I cannot see the problem.

[Evil_Giraffe]

Wait, is this resolved?

The type of the parameter that the expression is heading for isn't considered in resolving the type of the expression itself.

The type of a ternary expression is derived from the types of the two return values. The first (null) is of type void (well, that's not exactly a type, but you know what I mean, right?) and the second (Convert.ToInt16(drpStatus.SelectedItem.Value)) is of type int.

int and null are not comparable, therefore that expression is not legal. You need to give the compiler a hint, by casting the null to an 'int?'.

That way you're comparing an 'int?' to an int, which have a common type of 'int?'

[Bill Crawley]

Hi,

Although I didn't post my resolution, I needed to cast with Null.

(Int16?)null

So My complete test became.

drpStatus.SelectedItem.Value == "" ? (Int16?)null : Convert.ToInt16(drpStatus.SelectedItem.Value)