A Beech 200 aircraft operated by Transwest Air, was conducting medevac flight 911 from La Ronge, to Prince Albert, Canada with 7 persons on board. When the landing gear was selected down during the landing check at Prince Albert, the right main landing gear did not indicate down and locked. The flight crew interrupted the approach, climbed to the minimum sector altitude and circled over the airport while the emergency landing gear extension checklist was performed. However, the right main landing gear remained unsafe. The flight crew declared an emergency and consulted with the operator’s maintenance and flight operations. Following troubleshooting, the flight crew retracted the landing gear; however, the right main landing gear remained partially extended. The flight crew elected to land with the landing gear in the retracted position; consequently, the GEAR UP landing checklist was completed, passengers were briefed and ARFF was deployed for the landing on runway 26. While on short final before the flare, both engines were shutdown and the propellers were feathered. After the aircraft stopped adjacent to taxiway A, the crew and passengers evacuated without injuries. The aircraft sustained substantial damage to the flaps and landing gear doors, and was later slung onto a flatbed trailer and transported to a hangar. Inspection by the operator’s maintenance identified that the right main landing gear down lock latch had experienced a structural failure. Several segments of the down lock were found on the runway.