Gov. Charles S. Robb described it yesterday as one of the prime potential growth areas in Virginia.

John F. Herrity, chairman of the Fairfax County Board of Supervisors, anticipated the day when it would become "the most prosperous commercial center" in the state.

The subject of all the attention was a 5,000-acre chunk of land known as the Dulles Corridor, a parcel slated to be the site of a commercial building boom.

Bordered by I-66 and Rtes. 50 and 28, the area is attracting some of the most prestigious names in the high-tech market -- firms such as TRW Defense Systems Groups, Electronic Data Systems, Satellite Business Systems, the Verdix Corp. and AT&T -- that covet the land-rich and highly accessible western part of Fairfax County.

An estimated 500 people, mostly government officials, developers, bankers and real estate brokers, turned out yesterday for an elaborate luncheon at the center of all the coming construction -- the Dulles Business Park in Chantilly.

The glowing rhetoric used to describe the future development turned to concern when the ever-present issue of transportation was raised.

Kenneth L. McVearry, vice president of Coldwell Banker Real Estate Services, which hosted the event, called the area "potentially one of the most significant markets in the entire Washington area and, for that matter, on the Eastern Seaboard."

But he added that the critical Rte. 28, now a two-lane highway, would "turn into a moving parking lot" in as little as three years unless improvements are made.

Robb said he will support efforts to widen Rte. 28 to help facilitate the proposed development and to alleviate potential traffic problems in the area.

The governor hailed the efforts of county officials and the interest of developers in Northern Virginia. He said he has a "vested interest" in seeing projects such as the one near Dulles succeed since he is planning to move back to his McLean home to practice law when his term expires in January.

Vowing her assistance in acquiring funds for a highway expansion was State Del. Dorothy S. McDiarmid (D-Fairfax).

McDiarmid said she hopes the 1986 legislative session will mark an end to the longstanding feud between north and south over state funds and that the Northern Virginia delegation will succeed in convincing the rest of the legislature that "what is good for Northern Virginia is good for the state."

McDiarmid, who is in line to become House Appropriations Committee chairman if she is reelected in November, cautioned that her elevation to that position would not guarantee an unlimited flow of money to Northern Virginia. "It doesn't mean I'll have a cache of money in my pocket," she said of the chairmanship.

McVearry told the crowd that it was witnessing a development that will be noted for its "controlled growth" and that, within a few years, "will rival any market in the Washington metropolitan area."

McVearry said developers have been attracted by the relatively inexpensive land costs in western Fairfax and by easy access to Dulles Airport and the Dulles Toll Road.

He added that word has spread through the development community that there is a favorable building climate in Fairfax County, where, he said, the government assists rather than fights developers.

Herrity reaffirmed the local government's commitment to the building plans.

"The county has supported this kind of development in this area and will continue to do so," he said.