When inside a class, is it better to call its private members or its public properties? [duplicate]

Question

This is something that I've always wrestled with in my code. Suppose we have the following code:

public class MyClass {
    private string _myVariable;

    public string MyVariable {
        get { return _myVariable; }
        set { _myVariable = value; }
    }

    public void MyMethod() {
        string usingPrivateMember = _myVariable; // method A
        string usingPublicProperty = MyVariable; // method B
    }
}

Which way is more correct - method A or B? I am always torn about this. Method A seems like it would be minutely faster, due to the fact that it doesn't have to go access a property before getting the real variable. However, method B is safer because if the getter for MyVariable gets business logic added to it, you are safe by always calling it, even if there is no current business logic.

What's the general consensus?

Answer 1

Use the property.

I think the property should be wholly responsible for managing that field.

There are plenty of implementations where it won't matter, but there are lots where it does matter -- a lot. Plus, this can be a bit of a pain to track down, because it always looks right.

You'll go wrong calling the property far fewer times than calling the field, and where there are exceptions to this rule, document the rationale.

Answer 2

This would really depend on what you are accessing the property for. Consider the following two scenarios:

Scenario 1: you write a method to provide a common action on the data in the class:

// assume a hypothetical class Position

public class Circle
{
    private int _radius;
    private int _xpos;
    private int _ypos;

    public int Radius { get { return _radius; } }
    public Position Center { get { return new Position(_xpos, _ypos); } }

    public bool PointInCircle(Position other)
    {
         return distance(this.Center, other) < this.Radius;
    }
}

Clearly the behavior of PointInCircle should be the same as if the user executed the code inside it. Therefore, it makes sense to use the public properties.

Scenario 2: you write a method to manipulate the underlying data. A good example of this is serialization. You would want to serialize the underlying data members as opposed to the values returned by property accessors.