C# - Get The Index Of The Item In The Collection After Productpage_rec?

getting an the index of a collection. Here is the code I'm using.

System.Text.StringBuilder sb = new System.Text.StringBuilder();

for (int i = 1; i < _prod.ActiveProductItemCollection.Count; i++)
{

sb.Append("<script type='text/javascript'>");[code]....

What I want to do is get the index of the item in the collection after productpage_rec.

So for instance, the first product would generate like


mboxCreate("product_productpage_rec1"

and so on and so forth for each product in the collection. When I try to build I get the follwong error:

"cannot convert from string to char"

Its tripping up on the product_productpage_rec{0}