public virtual void Save()
{
// Check that a filename has been specified
if (_filename == null || _filename.Length == 0)
throw new MobiEPUBexception("Save failed: no filename specifed");
// Check that the metadata is valid:
// 1. Has a title been specifed?
if (_meta.Title == null || _meta.Title.Length == 0)
throw new MobiEPUBexception("Save failed: no title specified");
}