The string containing the regular expression used to filter the text field string. A value of null (Nothing in VB) means no regular expression pattern matching will be performed on this field.
Using a regular expression does not change the results of the processing. However, the value of the TextFormFieldResult.IsValidated property of the TextFormFieldResult object will determine whether the text read matches the specified regular expression.
For an example, if you set TextFormField.RegexPattern to a date expression such as "MM-DD-YYYY" and the value of the result text in OcrFormFieldResult.Text is "9 12 09", then the regular expression is not matched and the value of TextFormFieldResult.IsValidated will be false. If however, the value of the result text is "09-12-2009", then the regular expression is matched and the value of TextFormFieldResult.IsValidated will be true.