Mayor Marion Barry yesterday requested an investigation of a dinner held here Friday night in the apparent expectation that he would participate although he said he had made it clear he could not come.

In a statement released last night, the mayor said he has asked Audrey Rowe, his assistant on youth affairs, "to look at all aspects surrounding" what was planned as a semiformal dinner dance created by a nonprofit advisory group of the mayor's social and political allies. Reportedly Barry was to receive an award at the dinner.

The affair at the Shoreham Americana was billed as the triumphant culmination of the mayor's 1979 summer youth employment program. No more than 200 or so of the 1,000 persons expected arrived. Dinner was 1 1/2 hours late. A place set at the head table for the mayor remained empty all evening.

According to last night's statement, Barry's appointment's secretary had advised the dinner's sponsors two weeks ago and again last Wednesday that the mayor's schedule would prevent him from attending.

Barry was reported particularly concerned about possible disappointment of any youths who might have expected him to attend and about the possiblity that donors of goods or services may have been influenced by a similar expectation.