85

What is the equivalent in VB.NET of the C# As keyword, as in the following?

var x = y as String;
if (x == null) ...
Stephen Kennedy
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JoelFan
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7 Answers7

110

It is TryCast:

Dim x As String = TryCast(y, String)
If x Is Nothing Then ...
nloewen
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Hans Passant
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    +1 Although I believe `TryCast` is not **exactly** equivalent to `as` because `TryCast` doesn't work for value types? – MarkJ Mar 15 '10 at 23:24
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    @Mark: The *as* operator doesn't work on value types in C# either. – Hans Passant Mar 16 '10 at 00:11
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    Well it works for nullable value types... You can do: var x = y as int?; if (x == null) ... so you should be able to do Dim x = TryCast(y, System.Nullable(Of Integer)) in VB – JoelFan Mar 16 '10 at 01:41
  • @JoelFan, @nobugz. Oops. Let's try again. I believe `as` can convert value types into **nullable** types but `TryCast` can't? http://stackoverflow.com/questions/746767/how-to-acheive-the-c-as-keyword-for-value-types-in-vb-net/746914#746914 – MarkJ Mar 16 '10 at 13:52
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    This only works in very select cases because C# automatically applies a boxing conversion to "y". It cannot convert, say, a double to an int? – Hans Passant Mar 16 '10 at 15:19
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    @HansPassant C# will hardly ever "implicity" convert one primitive type (or any type) to another, you use the Convert.ToXXX method – enorl76 Aug 16 '14 at 20:04
9

Trycast is what you're looking for.

Dim x = TryCast(y, String)
Stewbob
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Morten Anderson
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6

TryCast:

Dim x = TryCast(y, String)
if (x Is Nothing) ...
Guffa
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6

Here you go:

C# code:

var x = y as String;
if (x == null) ...

VB.NET equivalent:

Dim x = TryCast(y, String)
If (x Is Nothing) ...
Alex Essilfie
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4

Dim x = TryCast(y, [String])

Oskar Kjellin
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3
Dim x = TryCast(y, [String])

From: http://www.developerfusion.com/tools/convert/csharp-to-vb/

Dustin Laine
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0

You can use it with ?:

TryCast(item, String)?.Substring(10)

It allows you to manage nullable without if :)

Stephen Kennedy
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evanboissonnot
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