添加文件扩展名？

Question

我想在附件中获取文件的扩展名，不确定如何执行此操作，下面是我的代码，在mailMessage.Add中添加输入流，文件名如何添加扩展名？ 下面是我的代码

if (unauthenticatedEnquiryViewModel.File != null) // this finds overall null
{
    foreach (var file in unauthenticatedEnquiryViewModel.File) // loop through every File
    {
        if (file != null) //Finds induvidual null
        {
            mailMessage.Attachments.Add(new Attachment(file.InputStream, file.FileName, file.);

            mailMessage.Body = mailbuilder.ToString();
         }
     }
 }

Answer 1

var extension = new FileInfo(file.FileName).Extension.ToUpper();

然后传入

mailMessage.Attachments.Add(new Attachment(file.InputStream, file.FileName, extension));