The extension that should be used when saving this template; based on the input file.

public String SaveExtension { get; }
Public ReadOnly Property SaveExtension() As [String]

The extension does not include the dot, such as "docx" or "dotm". Until a file is opened this will be null.

wordTemplate.Save("output." + wordTemplate.SaveExtension);
wordTemplate.Save("output." & wordTemplate.SaveExtension);