you can, with some exceptions. although those exceptions are getting further and further apart.
Someone will correct me but the ratio for DME to Grain is .6:1 approximately.
The general procedure is to identify those malts that must be mashed and see if you can replace them with extract at that .6:1 ratio.
So, my Kolsch recipe is about 7 lbs of pilsner and about 3 lb of munich malt. This all must be mashed and luckily you can find both pilsner DME and Munich LME) so you would want about 3-4 lbs pilsner extract and about 1.5-2 lbs munich extract.
Now this won't be exact because I don't think the munich extract is 100% munich but it will get you close.
If there is crystal malt in a recipe you can just leave that as is or reduce it a little because extract usually already has some crystal malt in it.