Overloading properties in C#

Question

Ok, I know that property overloading is not supported in C# - most of the references explain it by citing the single-method-different-returntype problem. However, what about setters? I'd like to directly assign a value as either a string or object, but only return as a string.

Like this:

    public string FieldIdList
    {
        get { return fieldIdList.ToString(); }
        set { fieldIdList = new FieldIdList(value); }
    }

    public FieldIdList FieldIdList 
    {
        set { fieldIdList = value; }
    }
    private FieldIdList fieldIdList;

Why wouldn't this be allowed? I've also seen that "properties" simply create getter/setter functions on compile. Would it be possible to create my own? Something like:

    public void set_FieldIdList(FieldIdList value)
    {
        fieldIdList = value;
    }

That would do the same thing. Thoughts?

Answer 1

Properties are in fact a pair of get/set methods (one of which may be left out), but the property itself has additional metadata which makes it a property in the first place instead of just two methods.

Because the property signature remains invalid as per only-different-by-return-type, even if you only have a setter. If you need this, don't use a property; set-only properties aren't a good thing anyways.

Answer 2

Its not allowed because of what you already stated in your question, for C# is not designed for that scenario. No overloaded reuse of names are possible because C# is a strongly typed language and does not allow implicit conversions.

Answer 3

One approach (you may argue amongst yourselves as to whether this is a good design choice or not) is to add a second property, which accesses the data in a different form.

However, as it is going to be parsing the string (doing significant work), it would be better not to use a property for this, but to add methods that allow you to get/set the data in a string form.

I'd go for fieldIdList providing ToString() and TryParse() interfaces - then if you need it as a string, you'd call myObject.FieldIdList.ToString() etc. This encapsulates everything tidily, allows you to convert to/from string formats anywhere in your code rather than only when accessing FieldIdLists as a member of some other class, and makes the client code really clear and easy to understand.

Answer 4

You can achieve your goal by writing something along these lines.

class Bar
{
    private string _foo = null;

    /// <summary>
    /// Gets or sets Foo. Set requires string or Foo object. Get returns string.
    /// </summary>
    public object Foo
    {
        get { return _foo; }
        set
        {
            if (value is string)
                _foo = (string)value;
            else if (value is Foo)
                _foo = value.ToString();
            else
                throw new ArgumentException("Must use string or Foo object");
        }
    }
}

class Foo
{
}

Answer 5

If you want to be able to set a property as either a string or an object then you would just use object as the type of the property, since it's the base class (you can pass a string to a property that accepts an object). This doesn't seem particularly good design decision, but it can be done. Perhaps you need to explain further what you are trying to achieve?