var table = new DataTable();

            var index = table.DefaultView
                .Cast<DataRowView>()
                .FirstIndex(r => ((int)r["id"]) == 12345);

    ............................................

    public static class EnumerableHelper
    {
        public static int FirstIndex<T>(this IEnumerable<T> src, Func<T, bool> match)
        {
            int result = 0;
            foreach (var item in src)
            {
                if (match(item))
                    return result;
                result++;
            }
            return -1;
        }
    }

public class DataView : MarshalByValueComponent, IBindingList,
   IList, ICollection, IEnumerable, ITypedList, ISupportInitialize
{
    ....
}

((int)r["id"]) == 12345

int index = table.Rows.IndexOf(table.DefaultView.Cast<DataRowView>().First(item => (int)item["ID"] == 123).Row);

var index = table.DefaultView.Cast<DataRowView>().Select((item, index) => new { id = (int)item["ID"], index }).Single(search => search.id == 123).index;