Getter and Setter declaration in .NET

Question

I was wondering what were the differences between those declaration of getters and setters and if there is a preferred method (and why). The first one can be generated automaticly by Visual Studio. How about the others ? Thanks

1st

string _myProperty { get; set; }

2nd

string _myProperty;

public string myProperty
{
    get { return _myProperty; }
    set { _myProperty = value; }
}

3rd

string _myProperty;

public string getMyProperty()
{
  return this._myProperty;
}

public void setMyProperty(string value)
{
  this._myProperty = value;
}

Answer 1

Properties are used to encapsulate some data. You could use a plain field:

public string MyField

But this field can be accessed by all outside users of your class. People can insert illegal values or change the value in ways you didn't expect.

By using a property, you can encapsulate the way your data is accessed. C# has a nice syntax for turning a field into a property:

string MyProperty { get; set; }

This is called an auto-implemented property. When the need arises you can expand your property to:

string _myProperty;

public string MyProperty
{
    get { return _myProperty; }
    set { _myProperty = value; }
}

Now you can add code that validates the value in your setter:

set
{
    if (string.IsNullOrWhiteSpace(value))
        throw new ArgumentNullException();

    _myProperty = value;
}

Properties can also have different accessors for the getter and the setter:

public string MyProperty { get; private set; }

This way you create a property that can be read by everyone but can only be modified by the class itself.

You can also add a completely custom implementation for your getter:

public string MyProperty
{
    get
    {
        return DateTime.Now.Second.ToString();
    }
}

When C# compiles your auto-implemented property, it generates Intermediate Language (IL). In your IL you will see a get_MyProperty and set_MyProperty method. It also creates a backing field called <MyProperty>k_BackingField (normally this would be an illegal name in C# but in IL it's valid. This way you won't get any conflicts between generated types and your own code). However, you should use the official property syntax in C#. This creates a nicer experience in C# (for example with IntelliSense).

By convention, you shouldn't use properties for operations that take a long time.