At the conclusion of a cross-country flight, the pilot announced his position as he was approaching the non-towered airport with the intention to conduct a straight in approach to runway 35. The landing was normal, and the pilot reported that there was "at least" 4,000 feet of runway remaining after touchdown. During the landing roll, when the airplane had slowed to about 50 knots, he decided to retract the flaps. However, he inadvertently grasped and raised the landing gear handle instead, and the nose gear retracted. The main gear remained extended, and the airplane came to a stop on the runway. The airplane sustained substantial damage to the nose keel structure, as well as damage to the cowl, nose gear doors, and propeller. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot further reported, “When landing, pilot should make no changes to flaps or other systems until the airplane has fully decelerated.”