UiPath-ADPv1 Advanced Debugging Practice Question
Exhibit
Error: The source contains no DataRows. Source: Assign. Message: Exception has been thrown by the target of an invocation.
Refer to the exhibit. You encounter this error while executing a Linq query on a DataTable. Which debugging strategy is the most effective way to identify the cause?
⚠ Common exam trap
Candidates often assume the Linq query will always return a row, failing to account for empty DataTables, which causes the First() method to throw an immediate exception.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the Locals panel to check the 'Rows.Count' property of the DataTable before the assignment.
This error typically occurs when a Linq method like 'First()' or 'Single()' is called on an empty collection, as these methods expect at least one result. By adding a breakpoint before the assignment and inspecting the DataTable count in the Locals panel, you can confirm if the query produced any results. This helps verify your filtering logic or confirm if the source data is unexpectedly empty before processing occurs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the 'Retry Scope' count on the activity.
Why it's wrong here
Increasing the retry count is ineffective here because the error is logic-based, not transient. If the source DataTable is empty, retrying will consistently fail with the same exception. Logic errors must be resolved by fixing the data filtering criteria or adding proper collection checks before processing.
- ✓
Use the Locals panel to check the 'Rows.Count' property of the DataTable before the assignment.
Why this is correct
The Locals panel allows you to inspect the object's properties in real-time. By checking the Rows.Count, you verify if the data exists. If the count is zero, you immediately know the Linq query is targeting an empty set, allowing you to implement a safety check.
- ✗
Change the execution mode to 'Debug' and run from start.
Why it's wrong here
Running from the start is inefficient for large processes. If the error happens at a specific point, you should use the 'Run to this Activity' feature. Simply restarting the process does not provide any insight into the state of the DataTable or why the data is missing.
- ✗
Wrap the entire sequence in a 'Parallel' activity.
Why it's wrong here
Wrapping code in a Parallel activity introduces concurrency complexity and does not fix the underlying issue of an empty source collection. It complicates the debugging process without addressing the root cause, which is a logic failure triggered by an empty collection in a Linq operation.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official UiPath exam blueprint
This UiPath-ADPv1 practice question is part of Courseiva's free UiPath certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the UiPath-ADPv1 exam.