What is the use of the := syntax?

Question

I'm a C# developer working on a VB.NET project, and VS keeps trying to get me to use the := thingie when I call a function with a ByRef parameter like so:

While reader.Read()
HydrateBookFromReader(reader:=???)

the HydrateBookFromReader function has the following signature:

Public Function HydrateBookFromReader(ByRef reader As SqlDataReader) As Book

Why does intellisense keep insisting that I use that := construction, and what is it for?

Answer 1

In VB, the := is used in specifying named parameters.

Contact(Address:="2020 Palm Ave", Name:="Peter Evans")

This is especially useful for specifying optional parameters.

Answer 2

Why does intellisense keep insisting that I use that := construction, and what is it for?

It's important to note that IntelliSense doesn't insist, it proposes. Using it in your case wouldn't make sense … this feature is primarily used for very long parameter lists with many optional parameters, of which you only want to pass, say, the last one. It's useful when working with Microsoft Office Interop.

Also (since you mention it in your tags): this has got nothing to do with ByRef. ByRef is equivalent to ref and out in C#, i.e. it allows the method to manipulate the parameter itself.