Why should I avoid using Properties in C#?

Question

In his excellent book, CLR Via C#, Jeffrey Richter said that he doesn\'t like properties, and recommends not to use them. He gave some reason, but I don\'t really understand

Answer 1

It's just one person's opinion. I've read quite a few c# books and I've yet to see anyone else saying "don't use properties".

I personally think properties are one of the best things about c#. They allow you to expose state via whatever mechanism you like. You can lazily instantiate the first time something is used and you can do validation on setting a value etc. When using and writing them, I just think of properties as setters and getters which a much nicer syntax.

As for the caveats with properties, there are a couple. One is probably a misuse of properties, the other can be subtle.

Firstly, properties are types of methods. It can be surprising if you place complicated logic in a property because most users of a class will expect the property to be fairly lightweight.

E.g.

public class WorkerUsingMethod
{
   // Explicitly obvious that calculation is being done here
   public int CalculateResult()
   { 
      return ExpensiveLongRunningCalculation();
   }
}

public class WorkerUsingProperty
{
   // Not at all obvious.  Looks like it may just be returning a cached result.
   public int Result
   {
       get { return ExpensiveLongRunningCalculation(); }
   }
}

I find that using methods for these cases helps to make a distinction.

Secondly, and more importantly, properties can have side-effects if you evaluate them while debugging.

Say you have some property like this:

public int Result 
{ 
   get 
   { 
       m_numberQueries++; 
       return m_result; 
   } 
}

Now suppose you have an exception that occurs when too many queries are made. Guess what happens when you start debugging and rollover the property in the debugger? Bad things. Avoid doing this! Looking at the property changes the state of the program.

These are the only caveats I have. I think the benefits of properties far outweigh the problems.