What is the ruling on a Christian declaring his conversion to Islam in order to marry a Muslim woman, and what are the conditions for his true conversion to Islam?

Scholars are in agreement regarding the prohibition of a disbeliever marrying a Muslim woman, based on the Almighty's saying: "And do not marry [your women] to idolaters until they believe." However, it is permissible for him to marry her after he embraces Islam, pronounces the two testimonies (Shahadatayn), and commits to the outward rulings of Islam.