Dear Sir/Madam, a director of our Company wishes to visit Canton Fair 2012 (Summer).

You can apply for an official invitation from the official website of the Canton Fair 2012, since it is necessary for your China visa application.
Besides the letter, you also need to present the valid Sri Lanka passport of director, completely filled visa application form and round-trip air ticket. Other documents may be also requried such as a covering letter from your company to state the position, salary and travel purpose of your director.