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# CheckPrefix Method of the IExternalDictionary Interface

This method is implemented on the client-side. This method determines if the dictionary contains a word with the specified prefix. It must return TRUE, if the dictionary contains at least one word with the prefix which is specified as a [fuzzy string](/fine-reader/engine/api-reference/language-related-objects/fuzzystring). This method is called during recognition of difficult cases, if the [CheckPrefixes](/fine-reader/engine/api-reference/language-related-objects/externaldictionarydescription#checkprefixes) property of the [ExternalDictionaryDescription](/fine-reader/engine/api-reference/language-related-objects/externaldictionarydescription) object is set to TRUE.

## Syntax

### C++

```cpp theme={null}
HRESULT CheckPrefix(
  IFuzzyString* Prefix,
  VARIANT_BOOL* Result
);
```

### C\#

```csharp theme={null}
bool CheckPrefix( IFuzzyString Prefix );
```

### Visual Basic .NET

```vb theme={null}
Function CheckPrefix( Prefix As IFuzzyString ) As Boolean
```

## Parameters

Prefix

\[in] This parameter contains the fuzzy string.

Result

\[out, retval] This parameter is TRUE if the dictionary contains at least one word with the prefix which is specified in the Prefix parameter as a fuzzy string.

## Return values

\[C++ only] If this method returns a value other than S\_OK, it indicates that an error occurred on the client-side.

## Remarks

* The pointer to the [FuzzyString](/fine-reader/engine/api-reference/language-related-objects/fuzzystring) object which was used as the Prefix parameter is released automatically after the end of the CheckPrefix method execution, therefore you do not need to call the Release method for this object in the CheckPrefix method implementation.
* 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

[IExternalDictionary](/fine-reader/engine/api-reference/language-related-objects/iexternaldictionary-interface)