Converting VB's IIf to Conditional Operator in c#

Michael9000

It's been a while since I've used VB and I need help with understanding the truePart in the second line.

Dim asciiBytes As Byte() = Encoding.ASCII.GetBytes("SomeAsciiData")

Dim nextchar As Integer = IIf(asciiBytes.Length > (i + 1), asciiBytes.Length > (i + 1), -1)

How does asciiBytes.Length > (i + 1) return an integer?

Geoff Williams

In VB.NET an expression like

asciiBytes.Length > (i + 1)

will return a Boolean value - in this case True as it is identical to the Expression part of the IIf method. Internally, a Boolean value is stored as an integer (False -> 0, True -> -1), so the conversion to an integer is straightforward. However, I think there' a bug in your code: it should probably read

Dim nextchar As Integer = IIf(asciiBytes.Length > (i + 1), asciiBytes(i + 1), -1)

in other words it returns the ASCII value (0 - 255) of the next character in the array if the Expression is True and -1 if it is False.

Michael9000

Thanks Geoff I didn't write the code (but that line is working) - maybe the compiler converts the boolean to a 0 or 1 in the background. I'll test it later

Lost User

Correctly, true equals -1, and 0 equals to false. Perhaps it would be easier to just initialize the variable to -1?

I are Troll :suss:

Michael9000

Absolutely right. :thumbsup: (I incorrectly assumed that true would be 1 and not -1)