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# OnReadPages Method of the IDocumentViewerEvents Interface

> OnReadPages method of the IDocumentViewerEvents Interface in ABBYY FineReader Engine Visual Components on Windows — This method is implemented on the client-side.

This method is implemented on the client-side. It is called by ABBYY FineReader Engine before the start of the page recognition process which has been invoked from [Document Viewer](/fine-reader/engine/visual-components-reference/documentviewer) in one of the following ways:

* Read Page item in the context menu is selected
* Ctrl+R hot key is pressed
* [MI\_Read](/fine-reader/engine/visual-components-reference/documentviewer/document-viewer-commands#mi_read) command is called using the [DoCommand](/fine-reader/engine/visual-components-reference/supplementary-objects/commands/docommand-method) method of the IDocumentViewer::Commands

It informs the client that selected pages are going to be recognized. With the help of this method it is possible to cancel the operation.

## Syntax

### C++

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

### C\#

```csharp theme={null}
void OnReadPages( out bool Cancel );
```

### Visual Basic .NET

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

## Parameters

Cancel

\[out] You may set this variable to TRUE to indicate that the process should be terminated. In this case, recognition will not be performed.

## 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

[IDocumentViewerEvents](/fine-reader/engine/visual-components-reference/idocumentviewerevents)