When writing a thank you card in response to an invitation to a dinner or any other event, a person should include a greeting, show thanks for the invitation, include details about attendance and end with a phrase showing regards. The thank you card tells the person who sent the invitation that the recipient is appreciative and provides details on whether he is attending the dinner.
The card should start with a warm greeting that includes the names of anybody involved in sending the invitation. The card writer should then say "thank you" in a personal way that shows appreciation for being invited. The card should include specific details on whether the person will attend the dinner. It's also a good idea to state the time and date of the dinner. The end of the card should include both a restating of the person's thanks for the invite and a concluding salutation.