Перегрузка операторов в C#

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сэр
Я написал код для перегрузки оператора, но он не работает.
вот программа :
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using System;
class space
{
    int x, y, z;
    public space(int a, int b, int c)
    {
        x = a;
        y = b;
        z = c;
    }
    public void display()
    {
        Console.Write("" + x);
        Console.Write("" + y);
        Console.Write("" + z);
    }
    public static space operator -(space s)
    {
        s.x = -s.x;
        s.y = -s.y;
        s.z = -s.z;
    }
}
 class TestMain
 {
     public static void Main()
     {
         space s = new space(10, -20, -40);
         Console.Write("S:");
         -s.display();
         Console.Write("S:");
         Console.Write("S:");
         -s.display();
     }

 }
it shows the following errors:
Error	1	'space.operator -(space)': not all code paths return a value	C:\Users\LENOVO PC\Documents\Visual Studio 2010\Projects\operator_overload\operator_overload\Program.cs	17	25	operator_overload
Error	2	Only assignment, call, increment, decrement, and new object expressions can be used as a statement	C:\Users\LENOVO PC\Documents\Visual Studio 2010\Projects\operator_overload\operator_overload\Program.cs	30	10	operator_overload
Error	3	Operator '-' cannot be applied to operand of type 'void'	C:\Users\LENOVO PC\Documents\Visual Studio 2010\Projects\operator_overload\operator_overload\Program.cs	33	10	operator_overload
Error	4	Only assignment, call, increment, decrement, and new object expressions can be used as a statement	C:\Users\LENOVO PC\Documents\Visual Studio 2010\Projects\operator_overload\operator_overload\Program.cs	33	10	operator_overload

What I have tried:

sir  i have tried 
-s.display() 
but no results..

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