Debugging Large Loops in D365 F&O

 When you are new to D365 Finance & Operations (or X++), debugging can feel overwhelming — especially when your code runs inside large loops.

Let me start with a situation almost every beginner faces.

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The Common Beginner Problem

You write code like this:

while select employee
{
    employeeId = employee.PersonnelNumber;

    // complex logic
} 

Now imagine:

• The loop runs for hundreds of employees
• A bug happens only for one employee (E0001)

You put a breakpoint inside the loop…

And then:

• The debugger stops again and again
• You keep pressing F5
• You lose focus and patience

This is normal when you are starting out.

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What I Used to Do Earlier (Many Beginners Still Do)

Earlier in my career, I used this trick:

if (employeeId == 'E0001')
{
    int x = 0;   // breakpoint here
} 

It works — the debugger stops only for that employee

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The Right Tool: Conditional Breakpoints

Visual Studio allows you to put a condition on a breakpoint.

Meaning:

“Stop execution only when a condition is true”

And the best part? 👉 No code change required

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How to Add a Conditional Breakpoint (Step-by-Step)

1. Put a breakpoint on the required line
2. Right-click the breakpoint → Conditions
3. Enable Conditions
4. Enter the condition:

employeeId == "E0001" 

Now the debugger will:

• Skip all other employees
• Stop only when E0001 is processed

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⚠️ Very Important for Newbies: String Syntax Gotcha

In X++ code, this works:

if (employeeId == 'E0001') 

But in a conditional breakpoint, this does NOT work:

employeeId == 'E0001'   ❌ 

Why?

Because the debugger treats single quotes as a character, not a string.

✅ Always use double quotes in debugger conditions:

employeeId == "E0001" 

Or even safer:

strCmp(employeeId, "E0001") == 0 

This small detail can save you a lot of confusion.

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Where Should You Place the Breakpoint?

Always place it after the value is assigned:

employeeId = employee.PersonnelNumber;
// breakpoint here 

If you place it before assignment, the condition will never be true.