Converting arrays - from VBA to C# (Best Practice)

Question

I have converted about 4000-5000 lines of code from VBA to C#. The only issue I have is the following:

In VBA you can create an array of a type and also set the start index. For example:

//This creates an Array with an index 5 to index 100.
doubleArray(5 To 100) As Double

It is not possible in C# to create an array that starts at an index other than 0. (See the link below.) In my opinion that will leave the following two possibilities:

1. Create a doubleArray from 0 to 100

I could create an doubleArray as follows:

Double[] doubleArray = new Double[100];

This has as an advantage that I can set the index by using the index number described as in the VBA code. This means the following; The VBA code assumes that the array exists from [5] to [100] and I am also able to set the number 5 to 100 in C#.

In my opinion however this is quite messy, because you will always create arrays with unused memory (in this case index [0] to index [4]). Because of this I was thinking of the second option.

2. Create a doubleArray from 0 to ((topindex - bottomindex) + 1)

I Could create a doubleArray as follows:

Double[] doubleArray = new Double[((topindex - bottomindex) + 1)];

In my opinion this should be the 'cleanest' way to overcome the problem, without unnecessary memory usage. In VBA the array uses [5] to [100], that makes the length 96. The same is the case for this option ( ((100 - 5) + 1) = 96 ).

However the big downside is that this would also require to overlook all the code that has already been written. If any function calls doubleArray[97], it should be doubleArray[((97 - 5) + 1)].

My question is thus, how to handle with this situation?

If anyone else sees another option/possibility, suggestions are more than welcome.

For some more background information. A follow-up from my earlier question: Vba Type-Statement conversion to C#

You could create a wrapper around the array with an indexer that could apply the offset. Optionally providing a way to use conventional 0-based indexing. — Jeff Mercado
– Jeff Mercado, Commented Aug 7, 2015 at 14:53
Technically you can create arrays from C# with non-zero lower bounds. I'd probably work to fire anyone who introduced such code into my workplace though. — Damien_The_Unbeliever
– Damien_The_Unbeliever, Commented Aug 7, 2015 at 14:54
@Damien_The_Unbeliever Like I said below, I did not write the source. — Revils
– Revils, Commented Aug 7, 2015 at 15:15

Bathsheba · Accepted Answer · 2015-08-07 14:43:13Z

3

Three steps:

Create unit tests around every instance of an array in VBA.
Adjust all the VBA arrays to be zero based, checking compliance with your unit tests.
Port to C#.

I'd be keen to avoid introducing errors across language boundaries, as it's more difficult to reconcile issues.

answered Aug 7, 2015 at 14:43

Bathsheba

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2 Comments

Revils Over a year ago

I like your solution very much, but it can be very hard to make the arrays zero based, since for example; 25 is the age, so at index [25] the double value is the result for somebody with age 25. (I did not write the source code myself, else I would've used classes.)

Bathsheba Over a year ago

That's what unit tests are for. Zero based arrays in C# are so idiomatic that everyone will expect a 1 + age notation for that particular array.

Cyyrils · Accepted Answer · 2015-08-07 15:39:45Z

1

I'd go for #2 but here is another solution I thought for you.

You can also do a custom class, with just an array inside. You will do 3 methods:

one to set an element( myObject.setElement(6,0.12) )
one to get an element( myObject.getElement(6) )
the first one to set the size of the array ( myObject.setSize(5,100) )

Actually when you will get or set the element, you will go to the index (index-5)

Example of class you can do

    public class CustomArray {
      private Double[] myArray;
      private int spread;

      public CustomArray(){
        setSize(5,100);
      }

      public void setSize (int lowerIndex, int upperIndex){
        myArray = new Double[(upperIndex-lowerIndex)+1]
        spread = lowerIndex
      }

      public Double getElement(int index){
        return myArray[index-spread];
      }

      public void setElement(int index, Double element){
        myArray[index-spread] = element;
      }
    }

(PS: It's been a year that I didn't program in C# so there might be a few syntax error but the code is for the better understanding)

answered Aug 7, 2015 at 15:39

Cyyrils

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2 Comments

Revils Over a year ago

I get the idea, it is like the wrapper class Jeff Mercado means. I will certainly try it!

Revils Over a year ago

One note to go with the wrapper class, it can seriously effect the performance of an application with some larger multidimensional arrays!

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