Using VB.NET IIF I get NullReferenceException

.net vb.net nullreferenceexception
Nathan Koop picture Nathan Koop · Jan 9, 2009 · Viewed 21.9k times · Source

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?

Answer

bdukes picture bdukes · Jan 9, 2009

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())

Related questions

What is a NullReferenceException, and how do I fix it?

I have some code and when it executes, it throws a NullReferenceException, saying: Object reference not set to an instance of an object. What does this mean, and what can I do to fix this error?

Read More
VB .Net NullReferenceException work-around

This should be simple, but I am having problems. Using the eBay .Net library, sometimes certain fields in a response are Nothing and sometimes contain a value. When they are Nothing they could simple be represented as an empty string, …

Read More
Why is Dictionary preferred over Hashtable in C#?

In most programming languages, dictionaries are preferred over hashtables. What are the reasons behind that?

Read More