Office PowerPoint:如何应用我通过 ActivePresentation.Designs.Add() 创建的新设计

Office PowerPoint: how to apply a new Design I created via ActivePresentation.Designs.Add()

我正在尝试创建新的幻灯片母版并将其应用于当前演示文稿,代码如下:

    var design = app.ActivePresentation.Designs.Add("my own design");
    app.ActivePresentation.Apply??

我试了 ApplyTheme 和 ApplyTemplate,它们都抛出异常

System.Runtime.InteropServices.COMException (0x80048240): Presentation (unknown member) : Invalid request.  PowerPoint could not open the file.
   at Microsoft.Office.Interop.PowerPoint.PresentationClass.ApplyTheme(String themeName)

有什么想法吗?提前致谢。

使用:

ActivePresentation.Slides.Range.Design = design