使用 Microsoft.Office.Interop.PowerPoint PPT转PDF的问题

转换的时候老是出现dos窗口，这个怎么隐藏掉啊？

 application = new PowerPoint.ApplicationClass();
            persentation = application.Presentations.Open(sourcePath, Microsoft.Office.Core.MsoTriState.msoTrue, Microsoft.Office.Core.MsoTriState.msoFalse, Microsoft.Office.Core.MsoTriState.msoFalse);
            persentation.SaveAs(targetPath, targetFileType,Microsoft.Office.Core.MsoTriState.msoTrue);