The Prime Avoidance Theorem is :
Let $I \subset R$ be an ideal (with $R$ commutative ring) and $I \subseteq \bigcup_{i=1}^r P_i$, where each $P_i$ is prime. Then $I \subseteq P_i$ for some $I$.
I want to find counter example of this does not hold in the case there are infinitely many prime ideals.
I often see this example in the case of $R=\Bbb C[x,y]$, but I want to find an example in the case $R$ is Dedekind domain.
Any good ideas ?
I tried with ring of integers of number field, but in vain. Thank you for your help.