My weight is not gaining.. what type of diet i should follow.. i am 27 and 52 kg only.. plz help..

Since I don't know: Your height, i can't make any calculations, but you are most likely not at an unhealthy weight. If you want to gain weight, eat a healthy, well-balanced diet and exercise daily. Consume 3500 calories more than you burn off to gain a pound. Don't try to do it all at once, but slow and steady. Learn to eat properly for the rest of your life. I assume you have been evaluated for chronic medical prob.