Try this:
public class Param<T>
{
private static readonly Func<T, T, T> addMethod;
static Param()
{
try
{
ParameterExpression left = Expression.Parameter(typeof (T), "left");
ParameterExpression right = Expression.Parameter(typeof (T), "right");
addMethod = Expression.Lambda<Func<T, T, T>>(Expression.Add(left, right), left, right).Compile();
}
catch (InvalidOperationException)
{
//Eat the exception, no + operator defined :(
}
}
public string param_name;
public T cnt;
public Param(T _cnt)
{
cnt = _cnt;
}
public static Param<T> operator +(Param<T> leftOperand, Param<T> rightOperand)
{
if (addMethod != null)
{
return new Param<T>(addMethod(leftOperand.cnt, rightOperand.cnt));
}
return null;
}
}
private static void Main(string[] args)
{
var pi = new Param<int>(5);
var pi2 = new Param<int>(6);
var pi3 = pi + pi2;
var pi4 = new Param<ooject>(5);//Wont work
var pi5 = new Param<object>(6);
var pi6 = pi4 + pi5;
}