Programming style: should you return early if a guard condition is not satisfied?

Question

One thing I\'ve sometimes wondered is which is the better style out of the two shown below (if any)? Is it better to return immediately if a guard condition hasn\'t been sat

Answer 1

If you dig through the .net-Framework using .net-Reflector you will see the .net programmers use style 1 (or maybe style 3 already mentioned by unbeli). The reasons are already mentioned by the answers above. and maybe one other reason is to make the code better readable, concise and clear. the most thing this style is used is when checking the input parameters, you always have to do this if you program a kind of frawework/library/dll. first check all input parameters than work with them.