I am doing a little debugging, and so I want to log the eventArgs value
I have a simple line that basically does:
logLine = "e.Value: " + IIf(e.Value Is Nothing, "", e.Value.ToString())
The way I understand the IIF function, if the e.Value is Nothing (null) then it should return the empty string, if not it should return the .ToString of the value. I am, however getting a NullReferenceException. This doesn't make sense to me.
Any idea's?
IIf is an actual function, so all arguments get evaluated. The If keyword was added to VB.NET 2008 to provide the short-circuit functionality you're expecting.
Try
logLine = "e.Value: " + If(e.Value Is Nothing, "", e.Value.ToString())
Nothing in VB is like default in C#, rather than null, so when used in a context where Boolean is the implied type, its value is False instead of null/Nothing as you'd typically think of it (per stackoverflow.com/q/1828173/2688). You'll need to cast one side of the If to the correct type (e.g. Boolean?) to get the desired result. Similarly in C#, you need to cast one side (but it's a compile error if you don't).VB does not do short-circuiting evaluation in Iif. In your case, e.Value.ToString() is being evaluated no matter whether e.Value is nothing.
If as the selected answer suggests.This is the expected behaviour.
IIF is a function; therefore the parameters for the function will be evaluated before sending it to the function.
In contrast, the ternary operator in C# is a language construct that prevents the evaluation of the second parameter if the expression of the ternary is true.
