String.Contains doesn't require parameters in c#?

Question

I've stumbled upon this code:

var knownSeparators = new[] { "\\", "/", "|", "." };
return knownSeparators.FirstOrDefault(path.Contains);

where path is a string and the return value should be a string as well.

Allthough path.Contains' intellisense suggests a parameter, it works fine without one.

How does this work exactly? Is there any way to copy this behavior in vb.net?

Jon Skeet · Accepted Answer · 2012-05-09 09:04:25Z

7

FirstOrDefault takes a delegate (a Func<T, bool>) and this call is creating a delegate from the method group. It's equivalent to:

Func<string, bool> predicate = path.Contains;
return knownSeparators.FirstOrDefault(predicate);

I suspect in VB.NET you could do:

Return knownSeparators.FirstOrDefault(AddressOf path.Contains)

... but I couldn't tell for sure without trying it.

answered May 9, 2012 at 8:55

Jon Skeet

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2 Comments

Sadly, it still gives the same error saying it requires a parameter (after adding the addressOf)

@djerry: I've edited to remove the brackets - see if that helps.