Question

Possible Duplicate:
Why do assignment statements return a value?

In C# you can use a property as both an lrvalue and rvalue at the same time like this :

int n = N = 1;

Here is a complete C# sample :

class Test
{
    static int n;

    static int N
    {
        get { System.Console.WriteLine("get"); return n; }
        set { System.Console.WriteLine("set"); n = value; }
    }

    static void Main()
    {
        int n = N = 1;

        System.Console.WriteLine("{0}/{1}", n, N);
    }
}

You can’t do that in C++/CLI as the resulting type of the assignment expression “N = 1” is void.

EDIT1: here is a C++/CLI sample that shows this :

ref class A
{
    public: static property int N;
};

int main()
{
    int n = A::N = 1;

    System::Console::WriteLine("{0}/{1}", n, A::N);
}

EDIT2: Moreover this is really confusing : what I was expecting was that the getter would be call to assign to n which is not the case at all; n directly receives the right-most value of the expression, i.e. 1 like shown by the generated CIL :

IL_0001:  ldc.i4.1
IL_0002:  dup
IL_0003:  call       void Test::set_N(int32)
IL_0008:  nop
IL_0009:  stloc.0

So what’s the magic behind C# syntax allowing a void-expression to be used as a rvalue ?

Is this special treatment only available for properties or do you know other C# tricks like this ?

EDIT : As pointed out C# assignment rules say that rvalue should ALWAYS be used as the return value of an assignment.

Answer 1

In C#, an assignment is the result of the assignment itself.

For example:

string a = null;

if((a = "hello world").Contains("world"))
{
      Console.WriteLine("It has 'world' word!");
}

As you see, it’s not about properties, but assignments.

An statement like this:

int n = N = 1;

…is equivalent to:

int n = (N = 1);

The point of this is (N = 1) has a return value itself: an integer value of 1.