Comprehensive Detailed Explanation
The method shown uses the Read API of the Azure Computer Vision client library. The ReadAsync call submits the OCR job and returns an Operation-Location header, which contains the operationId. Then GetReadResultAsync(Guid.Parse(operationId)) is called to fetch the result.
The Issue
The Read API is asynchronous.
Submitting the read request does not mean the OCR has finished.
If you immediately call GetReadResultAsync , the operation may still be in progress, resulting in incomplete or empty results.
Required Fixes
Check the results.Status property
The response from GetReadResultAsync includes a status property.
Possible values: notStarted , running , succeeded , failed .
You must wait until the status is succeeded before processing results.
This ensures you don't attempt to read lines before OCR has completed.
This corresponds to B.
Wrap in a loop with delay
Since OCR takes time, you need to poll the service until the status becomes succeeded or failed .
A typical pattern is:
ReadOperationResult results;
do
{
results = await client.GetReadResultAsync(Guid.Parse(operationId));
await Task.Delay( 1000 ); // wait 1 second before retrying
}
while (results.Status == OperationStatusCodes.Running || results.Status == OperationStatusCodes.NotStarted); This corresponds to D.
Option Analysis
A). Remove the Guid.Parse(operationId) parameter
Incorrect. The operationId is required to fetch the OCR results.
B). Add code to verify the results.Status value
Correct. You must check whether the operation has completed.
C). Add code to verify the status of the txtHeaders.Status value
Incorrect. txtHeaders only contains metadata and the operation location. The OCR completion status comes from the results.Status in the GetReadResultAsync response, not from txtHeaders .
D). Wrap the call to GetReadResultAsync within a loop that contains a delay Correct. This is how you poll until the operation has finished.
The answer: B and D
Microsoft References
Azure Computer Vision Read API
Read text using the Computer Vision client library