How to show files preview as a thumbnail in ASPxFileManager

This example is a simplified implementation of the DXDocs demo that illustrates how to create a file thumbnail based on the first page of the document. 
The ASPxFileManager.CustomThumbnail event is used for defining a custom value for the FileManagerItem.ThumbnailUrl property. Since this solution does not provide a cashing mechanism, previews are generated on each request. To increase application performance, refer to the FileSystemService class of the DXDocs demo.