Find the prime numbers according to the following conditions

I am working on a project related to DSA signature and need to generate two random primes in C#. The parameters I have are:

• P (1024 bits)
• Q (160 bits)
• The condition that (P-1) must be a multiple of Q.

I am not sure how to generate these primes as when I tried some normal algorithms, my program froze due to the large parameters. I would appreciate any help.

Thank you.