VSTO是一种.NET技术.这里不支持VB6问题.您可以在论坛的

VSTO is a .NET technology. VB6 questions are not supported here. You'll find a list of venues for non-VSTO, Office-related questions in the forum's Please Read First message. I recommend you ask in an Excel-specific venue. I suspect that you need to include a further parameter in the Open method that specifies the file format, but I don't know for sure.