Thread: Variable Properties vs Public Variables

I've read many books teaching the basics of C#,
and all of them (+ couple of ppl who told me the same thing) say that using properties of local variables instead of making methods to change private variables or just making the a public variable...

They all said it was "better programming".

But i want to understand why...

lets say i've made the following class

Code:

namespace exampleNamespace
{
  class exampleClass
  {
     int firstVar;
     int secondVar;
  }
}

now, i want to let another class initiate and change the vars' values.

so what's the difference between this code

Code:

namespace exampleNamespace
{
  class exampleClass
  {
     public int firstVar;
     public int secondVar;
  }
}

and this code

Code:

namespace exampleNamespace
{
  class exampleClass
  {
     int firstVar;
     public int FirstVar
     {get (return firstVar)
       set (firstVar = Value)}

     int secondVar;
     public int SecondVar
     {get (return secondVar)
       set (secondVar = Value)}
  }
}

i know you can write only the get part - but it's just like making it readonly...

and i never really understood why you have to make the local variables private when you make methods to change them....
what's the point in that? :P

Roy

The purpose of public properties or methods is to hide private data, and to maintain its integrity (encapsulation). You can also assign different access levels to the get or set to make them read-only, for example if you only want the value to be changed by the class's methods. Below is an example that shows why you would want to use properties, and also makes it so the property is only set from a private scope, in the constructor in this case.

Code:

namespace exampleNamespace
{
    public class exampleClass
    {
        double mAngle;
        public double Angle
        {
            get
            {
                return mAngle;
            }
            private set
            {
                value = value % 360;
                if (value < 0)
                    value += 360;
                mAngle = value;
            }
        }

        public exampleClass(double angle)
        {
            Angle = angle;
        }
    }
}

The reason you would want to make local variables private is so they're not modified when you don't want them to be. That is, they should only be modified by the classes methods or properties to ensure they're not corrupted. It is syntactically correct to make everything public, but in most cases it's a bad idea. The only time it would be smart is for very simple classes where any value is valid and it doesn't matter who changes it.

Thanks.