Question

How can you create a default – non indexer – property in C#?

What I mean by this is I can see that I can create indexer default properties as illustrated on this MSDN page.

This allows me to do things like

Widgets widgets = new Widgets();
Widget result = widgets[1];

But what if I want to achieve something like what Nullable<T> does?

Where you can take

Nullable<decimal> nullDec = 1.23m;
decimal result = nullDec.Value;

OR

decimal result = (decimal)nullDec;

Which I assume is simply a default property implementation to nullDec.Value???

Answer 1

Nullable<T> has special handling in the compiler, but you can do most of that by adding implicit or explicit static conversion operators.

For example, for type Foo you can add an operator:

public static implicit operator string(Foo value)
{
    return "abc";
}
public static implicit operator Foo(int value)
{
    ...
}

allowing:

Foo foo = ..
string s = foo; // uses string(Foo value)

and

int i = 123;
Foo foo = i; // uses Foo(int value)