Challenge 1: try/catch/finally, Then an Unchecked Custom Exception — Possible Solution
====================================================================

Program.cs:

class OutOfStockException : Exception
{
    public OutOfStockException(string message) : base(message) { }
}

static void DivideDemo()
{
    try
    {
        int result = 10 / 0;
        Console.WriteLine(result);
    }
    catch (DivideByZeroException e)
    {
        Console.WriteLine("Caught: " + e.Message);
    }
    finally
    {
        Console.WriteLine("This always runs.");
    }
}

// No throws-style declaration exists in C# at all -- this method
// compiles with zero warnings despite throwing.
static void ShipItem(int stock)
{
    if (stock <= 0)
        throw new OutOfStockException("No stock remaining.");
    Console.WriteLine("Shipped.");
}

DivideDemo();
ShipItem(0);   // uncaught -- crashes the program, but the CODE ITSELF compiled cleanly

Output:

    Caught: Attempted to divide by zero.
    This always runs.
    Unhandled exception. OutOfStockException: No stock remaining.
       at ShipItem(Int32 stock)
       ...

Explanation:
DivideDemo() behaves identically to java1-7's own try/catch/finally
shape. ShipItem(), by contrast, throws OutOfStockException with
absolutely no compile-time signal anywhere in its signature that it
might do so -- no throws clause exists in C# at all. The method
compiles cleanly regardless of whether callers handle the exception,
confirming the chapter's own claim that C# has no checked-exception
concept whatsoever.

WHY THIS WORKS AS AN ANSWER
------------------------------
This demonstrates both the familiar try/catch/finally shape shared
with java1-7 and, separately, a method throwing a custom exception
with zero compiler enforcement or warning, directly confirming the
chapter's central claim about C#'s unchecked-only exception model.