Custom Validation Sample Settings Custom validation: *.JPG *.PNG *.GIF *.BMP *.DOC *.TXT *.ZIP *.RAR Success files: Invalid files: Description Custom validation can be used to override the built-in validation using the sever-side ValidatingFile event. In order to validate whether a file is invalid or valid in the Validating event handler, set the IsValid of the ValidateFileEventArgs property to True for valid or False for invalid. Documentation