It was the practice of Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that when he was invited to a wedding feast (walimah), he would accept the invitation whether he was fasting or not. If he was fasting, he would supplicate for blessing, and if he was not fasting, he would eat.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصداق / 14534