// This method returns a plain text representation of a specified FlowDocument.
string GetTextFromFlowDocument(FlowDocument flowDoc)
{
     // Create a new TextRanage that takes the entire FlowDocument as the current selection.
     TextRange flowDocSelection = new TextRange(flowDoc.ContentStart, flowDoc.ContentEnd);

     // Use the Text property to extract a string that contains the unformatted text contents 
     // of the FlowDocument.
     return flowDocSelection.Text;
}