Hi Brandon. To answer your questions I am doing this in the code-behind and currently for K12 Portal Engine. However, after sleeping on it I figured it out. One needs to bind the data to the object in order to access the items. So I just added a repItems.DataBind(); to my method and then called the repItems.Items.Count. As follows for those looking for this answer:
public void CreateCarouselPager()
{
repItems.DataBind();
for (var i=0; i <= repItems.Items.Count; i++)
{
string pageCounter = string.Format("{0:D2}", i + 1);
lblCarouselPagerButtons.Text += "<button type=\"button\" data-nav=\"" + i + "\">" + pageCounter + "</button>" ;
}
}