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# OnProgress Method of the IAsyncProcessingCallback Interface

> OnProgress method of the IAsyncProcessingCallback Interface in the ABBYY FineReader Engine API — This method is implemented on the client-side.

<Note>
  This method is implemented in FRE for Linux and Windows.
</Note>

This method is implemented on the client-side. It is called by ABBYY FineReader Engine during processing with [Batch Processor](/fine-reader/engine/api-reference/batch-processor/batchprocessor). Its implementation can process system messages to help prevent the application from appearing unresponsive during long operations. The method allows you to cancel the operation.

## Syntax

### C++

```cpp theme={null}
HRESULT OnProgress( VARIANT_BOOL* Cancel );
```

### C\#

```csharp theme={null}
void OnProgress( ref bool Cancel );
```

### Visual Basic .NET

```vb theme={null}
Sub OnProgress( ByRef Cancel As Boolean )
```

## Parameters

Cancel

\[in, out] You may set this variable to TRUE to indicate that the process should be terminated. In this case, the processing function returns E\_ABORT.

## Return values

\[C++ only] If this method returns a value other than S\_OK, it indicates that an error occurred on the client-side, and in this case the value of the Cancel parameter is not taken into account.

## Remarks

The client implementation of this method must assure that all exceptions thrown inside the method are caught and handled and no exceptions are propagated outside the method. Propagation of an exception outside the method may lead to unpredictable results (such as program termination).

## See also

[IAsyncProcessingCallback](/fine-reader/engine/api-reference/batch-processor/iasyncprocessingcallback)

[BatchProcessor](/fine-reader/engine/api-reference/batch-processor/batchprocessor)