Short stem & riser bars on XC I found a crack under my handlebar and I'm thinking of buying a riser bar and a shorter stem for my mountain bike. is it a good idea? I don't ride on trails, not because i don't want to, I just don't have the chance to.Is it necessary to buy a riser bar &amp; a short stem on a XC hardtail?

Not sure if it's necessary but here is a picture of my bike I found on the internet.
Generally you can use any stem and bar you like, as long as they have the correct clamping diameters.

Be aware that you might need longer or shorter brake and shifter cables.

As a sidenote: I think often when people have the impression that there is too much weight on their hands it’s actually because their saddles are too low or in the wrong position. With a proper seating position roughly a third of your weight is on your hands, butt and feet each. With more intense riding it can be more than half your weight on your feet (this is one of the reasons why pro riders can ride such low bars and hard saddles).