What's the difference between a property with a private setter and a property with no setter?

Question

If I want a read-only property, I write it like:

public int MyProperty { get { //Code goes here } }

However, the Microsoft example (and a few other examples I've seen) are written like:

public int MyProperty { get; private set; }

Is there any difference between these two, and should I start writing properties like this?

Answer 1

As you can see in your second sample, you can leave out the implementation for a property. .NET will then automatically create a local variable for the property and implement simple getting and setting.

public int MyProperty { get; private set; }

is actually equivalent to

private int _myProperty;

public int MyProperty { 
    get { return _myProperty; }
    private set { _myProperty = value; }
}

Writing

public int MyProperty { get; }

does not work at all, as automatic properties need to implement a getter and a setter, while

public int MyProperty { get; private set; }

leaves you with a property that may return any int, but can only be changed within the current class.

public int MyProperty { get { ... } }

creates a read-only property.

Question is: what do you need? If you already have a member variable that's used within your class and you only want to return the current value using a property, you're perfectly fine with

public int MyProperty { get { return ...; }}

However, if you want a read-only property, which you need to set within your code (but not from other classes) without explicitly declaring a member variable, you have to go with the private set approach.

Answer 2

With private setter you can only assign property value inside of instance when property is without setter you can't set its value anywhere.