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# OnWarning Method of the IFRPageEvents Interface

This method is implemented on the client-side. It is called by ABBYY FineReader Engine for some of the methods of the [FRPage](/fine-reader/engine/api-reference/document-related-objects/frpage) object. It delivers to the client tips and warnings which occurred during processing.

<Note>
  In Windows, it can also process any system messages to help prevent the application from appearing unresponsive during long operations. This can be helpful in applications with a user interface.
</Note>

## Syntax

### C++

```cpp theme={null}
HRESULT OnWarning(
  IFRPage*      Sender,
  BSTR          Warning,
  VARIANT_BOOL* Cancel
);
```

### C\#

```csharp theme={null}
void OnWarning(
  IFRPage   Sender,
  string   Warning,
  ref bool Cancel
);
```

### Visual Basic .NET

```vb theme={null}
Sub OnWarning( _
  Sender As IFRPage, _
  Warning As String, _
  ByRef Cancel As Boolean _
)
```

## Parameters

Sender

\[in] Refers to the [FRPage](/fine-reader/engine/api-reference/document-related-objects/frpage) object which sends notifications.

Warning

\[in] Contains the tip or warning.

Cancel

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

[IFRPageEvents](/fine-reader/engine/api-reference/document-related-objects/ifrpageevents)

[FRPage](/fine-reader/engine/api-reference/document-related-objects/frpage)