Answer: If the questioner means by “before marriage,” before consummation of the marriage but after the contract, then there is no harm in such relations since she is his wife by virtue of the contract, even though they have not decorously consummated the marriage. However, if it is before the marriage, such as during the period of engagement or otherwise, such contact is forbidden and impermissible. It is not allowed for a man to enjoy a non-related women’s company, either by speech, look or private company. It is confirmed the Prophet (sallallaahu ‘alaihi-wasallam) said,
”A man cannot be alone with a women except in the presence of [one of her] mahram . And a women cannot travel except with a mahram .” 
In sum, if that contact or association is after contract, there is no harm in it. If it is before the marriage ceremony, even if it is after the proposal and acceptance, it is not allowed. Such behaviour is forbidden for him since the women is a non-relative and non-wife until they conclude the marriage contract.
 Recorded Muslim.Al-Bukhari has something similar.
Shaykh Muhammad bin Saalih al-`Uthaymeen
Islamic Fatawa Regarding Women – Darussalam Pg. 195-196