Create new Array of parameter type

Question

I'm trying to create a function to parse out all values in a multidimensional Array with all but one dimension given. The details are not relevant, but for this function I need to return an one-dimensional Array containing values of the same type the original multidimensional Array has.

To pass any Array with any dimension to my function, I declared the type of this parameter as Array. However, how would I create a new Array of that specific type (e.g. Integer)?

Currently I have the following code:

Function GetRow(ByVal arr As Array) As Array
    Dim result As (...) 'This should be Integer() if arr contains Integers, etc.
    Return result
End Function

How do I declare the type of result to make it having the same type of values as arr? New Array is not possible as it is declared MustInherit.

Can't give a good answer in VB.Net but this may help: msdn.microsoft.com/en-us/library/w256ka79.aspx — Austin Salonen
– Austin Salonen, Commented Jan 4, 2011 at 19:51

Hans Passant · Accepted Answer · 2011-01-04 19:52:41Z

4

Use generics here so the function can handle any type:

Function GetRow(Of T)(ByVal arr() As T) As T()
    Dim result() As T
    ReDim result(arr.Length - 1)
    Array.Copy(arr, result, arr.Length)
    Return result
End Function

Sample usage:

    Dim iarr() As Integer = {1, 2, 3, 4}
    Dim copy = GetRow(iarr)

answered Jan 4, 2011 at 19:52

Hans Passant

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3 Comments

pimvdb Over a year ago

Thanks a lot. However, this does not seem to be able to accept multidimensional Arrays. I guess this is because you declare the type of arr as arr(), i.e. a one-dimensional Array. Could you possibly explain what I could be doing wrong?

Hans Passant Over a year ago

Yes, you'll need another overload for multi-dimensional arrays. Declare the arrays as (,) for 2dim and tweak the code accordingly.

pimvdb Over a year ago

Okay, thanks. It's not fully generic, but I will only work with one, two or three-dimensional arrays anyway.

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