SharePoint列表附件，如何覆盖它们

关于SharePoint的快速问题。。。。 我需要使用SharePoint sdk更新列表上的附件，但每次删除旧附件并添加新附件时，都不会添加新文档。下面是我的代码

/* Delete the attachment first and create a new attachment.*/
            string fileName = newAttachmentName.Substring(0, newAttachmentName.IndexOf("."));
            //Delete Attachment
            SPAttachmentCollection attachments = item.Attachments;
            if (item.Attachments != null)
            {
                string oldfilename = attachments[0].ToString();

                attachments.DeleteNow(oldfilename);
                item.Update();
            }

            //AddAttachement(item, newAttachmentName, attachmentStream, true);
            attachments.Add(newAttachmentName, contents);
            ////attachments[0] = filename;
            item.Update();

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也许这会有所帮助：

以下内容不起作用：

SPAttachmentCollection attachments = listitem.Attachments;

foreach (SPFile file in attachments)
{
  // Do something
}

以下方法确实有效：

SPFolder folder = web.Folders["Lists"].SubFolders[list.Title].SubFolders["Attachments"].SubFolders[listitem.ID.ToString()];
foreach (SPFile file in folder.Files) 
{   
    // Something useful here 
}

---

也许这会有所帮助：

以下内容不起作用：

SPAttachmentCollection attachments = listitem.Attachments;

foreach (SPFile file in attachments)
{
  // Do something
}

以下方法确实有效：

SPFolder folder = web.Folders["Lists"].SubFolders[list.Title].SubFolders["Attachments"].SubFolders[listitem.ID.ToString()];
foreach (SPFile file in folder.Files) 
{   
    // Something useful here 
}

覆盖新文件的位置创建新附件实例（附件1）

---

覆盖新文件创建新附件实例（attachment1）

链接不会退出链接。没过多久就找到了：）链接没有退出链接。没过多久就找到了：）