If I understand this correctly.
Your modelseriesdropdown is a zero index array while your IEnumerable by default is a 1 index array.
So what if you tried to add 1 to modelseriesdropdown? then you know that it will match the IEnumerable index.
for each item in modelseriesdropdown
yourIEnumerableUiElement.ElementAt(cInt(item)+1) will fetch the first value in the dropdown.
I have used such index tricks before when I used an image match (many similar images in the same application). All the image properties were imported in an IEnumerable variable with
N length and with default 1 index. So what I did was to add 1 to my interested index so that I could get the 1st indexed value in the IEnumerable (which according to traditional programming is 0th index). This way you could also get the
Nth index value