Creating array on the fly as a parameter to a subroutine?

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Rob Nicholson

Consider the following example class:

Public Class ExampleClass
ReadOnly Property HelloWorld() As String
Get
Return "Hello, World"
End Get
End Property
End Class

And a subroutine:

Sub DoSomething(ec as ExampleClass)
End Sub

You can invoke this using:

DoSomething(New ExampleClass)

In that you don't need to create the parameter via variable. Is the same
possible with arrays as parameters:

Sub DoSomething(Words() As String)
End Sub

This can be invoked like this:

Dim MyWords() = {"Hello", "World", "Goodbye"}
DoSomething MyWords

However, is it possible to create an array on the fly like with something
like this:

DoSomething(New String()={"Hello","World","Goodbye"})

This doesn't work but gives an idea.

Cheers, Rob.

PS. I know about ParamArray Words() As String.
 
DoSomething(New String()={"Hello","World","Goodbye"})

Later...

Hmm, just done some experiments with ParamArray and discovered an
interesting side effect:

Dim MyWords() As String = {"Hello", "World", "Goodbye"}
Something(MyWords)

Sub Something(ByVal ParamArray MyWords() As String)
Dim x As String
For Each Word As String In MyWords
x &= Word & " "
Next
End Sub

The thing that surprised me about this is that I kind of expected VB.NET to
end up with MyWords() inside the sub containing just one item but this item
was itself an array. I have vague memories of this happening in VB6.

However, something different happens in that although only one parameter is
being passed, ParamArray MyWords() As String ends up containing 3 items
which is fine. So it means that when you use ParamArray you can either pass
a series of strings (in this example) or a single string array.

Taking it further:

Something(MyWords, "Wibble", "Wobble") generates a compile error complaining
that:

c:\inetpub\wwwroot\Hops\WebForm1.aspx.vb(32): Value of type '1-dimensional
array of String' cannot be converted to 'String'.

Which is kind of expected.

I assume this is intentional and programmed this way and not an accident of
some kind.

Cheers, Rob.

PS. Doesn't answer my original question though of whether you can create and
initialise arrays on the fly.
 
Rob Nicholson said:
Consider the following example class:

Public Class ExampleClass
ReadOnly Property HelloWorld() As String
Get
Return "Hello, World"
End Get
End Property
End Class

And a subroutine:

Sub DoSomething(ec as ExampleClass)
End Sub

You can invoke this using:

DoSomething(New ExampleClass)

In that you don't need to create the parameter via variable. Is the same
possible with arrays as parameters:

Sub DoSomething(Words() As String)
End Sub

This can be invoked like this:

Dim MyWords() = {"Hello", "World", "Goodbye"}
DoSomething MyWords

However, is it possible to create an array on the fly like with something
like this:

DoSomething(New String()={"Hello","World","Goodbye"})

This doesn't work but gives an idea.

Cheers, Rob.

PS. I know about ParamArray Words() As String.
Click to expand...
 
DoSomething(New String()={"Hello","World","Goodbye"})

Oh, I was so close :-) The syntax is actually:

DoSomething(New String() {"Hello", "World", "Goodbye"})

Didn't need the "=" character which you have to use when initialising a
variable:

Cheers, Rob.
 
Sub DoSomething(Words() As String)

End Sub

DoSomething(New String(){"Hello", "World", "Goodbye"})


hope that helps..
Imran.
 
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