How to convert full date/time to timestamp?

Which is more computationally expensive, trying to acquire a read/write lock or doing a few datetime comparisons?

• I have the following options in designing a block of code. In this design, we do a comparison and only if it's true we try acquiring the lock. if((DateTime.Now - timeStamp) < new TimeSpan(24,0,0)){ if(rwlock.tryWrite(4000)){ // blocks for 4s .... } } In this design, we first try acquiring the lock and only if we can we do the comparison. if(rwlock.tryWrite(4000)){ // blocks for 4s if((DateTime.Now - timeStamp) < new TimeSpan(24,0,0)){ .... } } I think it's best to put the less computationally expensive check first. So which check is less computationally expensive?

• Answer:

  Go for the first solution, for sure. Acquiring a lock implies much more work than a small bench of arithmetic operations. Moreover, if you have an heavy load, you'll avoid as contention as your test on dates is selective.