Return 'null' or throw exception

转自：http://stackoverflow.com/questions/175532/return-null-or-throw-exception

 

I have a method that is suppose to return an object if it is found.

If it is not found, should I:

a) return nullb) throw an exceptionc) other

if you are always expecting to find a value then throw the exception if it is missing. The exception would mean that there was a problem.
If the value can be missing or present and both are valid for the application logic then return a null.
More important: What do you do other places in the code? Consistency is important.