🧠 Mastering Boolean Logic & DateTime Conditions in C#

Conditional logic in C# is easy to write — but easy to get wrong when expressions grow more complex. I recently came across a test that combines boolean expressions, operator precedence, and DateTime comparisons. It’s a great opportunity to sharpen your understanding of how C# evaluates logic at runtime.

Here’s the test:

public static void Main()
{
    bool isForbidden = false;
    bool isActive = true;		
    bool isDelayed = true;

    DateTime threshold = DateTime.Now.AddDays(40);

    if (!isForbidden && isActive && DateTime.Now > threshold || !isForbidden && DateTime.Now.AddDays(35) < threshold)
    {
        Console.WriteLine("Not forbidden");
    }

    if (!isForbidden && isActive && DateTime.Now > threshold || (isDelayed && !isActive || (DateTime.Now.AddDays(35) > threshold || isActive)))
    {
        Console.WriteLine("Either delayed or not");
    }

    if (!isForbidden && isActive && DateTime.Now < threshold && !isDelayed)
    {
        Console.WriteLine("Not delayed");
    }
}

🔍 What Will Be Printed?

To evaluate this, let’s assume the code is running right now:

• threshold = now + 40 days

• DateTime.Now.AddDays(35) is before threshold

• DateTime.Now > threshold is false

• DateTime.Now < threshold is true

✅ First Condition:

if (!isForbidden && isActive && DateTime.Now > threshold || !isForbidden && DateTime.Now.AddDays(35) < threshold)

• !isForbidden && isActive && DateTime.Now > threshold → false

• !isForbidden && DateTime.Now.AddDays(35) < threshold → true

• false || true → true

🖨️ Output: Not forbidden

✅ Second Condition:

if (!isForbidden && isActive && DateTime.Now > threshold || (isDelayed && !isActive || (DateTime.Now.AddDays(35) > threshold || isActive)))

• !isForbidden && isActive && DateTime.Now > threshold → false

• isDelayed && !isActive → false

• DateTime.Now.AddDays(35) > threshold → false

• isActive → true

• Final expression: false || (false || true) → true

🖨️ Output: Either delayed or not

❌ Third Condition:

if (!isForbidden && isActive && DateTime.Now < threshold && !isDelayed)

• !isForbidden → true

• isActive → true

• DateTime.Now < threshold → true

• !isDelayed → false

• Entire condition: true && true && true && false → false

🖨️ Output: Nothing

✅ Final Console Output:

🎯 What You Should Learn From This

This code tests your understanding of complex boolean logic and how C# evaluates DateTime conditions dynamically. Here are some important takeaways:

💡 Key Lessons

1. Operator Precedence

   • && (AND) has higher precedence than || (OR)

   • Use parentheses to group logic clearly and avoid surprises

2. Short-Circuiting Behavior

   • With ||, if the first condition is true, the rest is skipped

   • With &&, if the first condition is false, the rest is skipped

3. DateTime Comparisons

   • DateTime.Now changes every time it’s called

   • If you want consistency, store DateTime.Now in a variable first

4. Write Readable Logic

   • For better maintainability, break complex conditions into variables or helper methods

👨‍💻 Final Thoughts

Even everyday conditions can become tricky when DateTime and multiple booleans are combined. Use this kind of test to practice reading logic like a compiler — left to right, obeying precedence, and anticipating short-circuiting.

Have you come across similar logical puzzles or real-world condition bugs? Let’s chat in the comments