您忘记复制项目的附件.看看这篇文章，部分下面重复了代码.

You forgot to copy the item's attachments. Have a look at this article, part of the code has been repeated below.

// ** Copy the fields
foreach(SPField field in sourceItem.Fields)
{
    if (newItem.Fields.ContainsField(field.InternalName) == true && 
        field.ReadOnlyField == false && field.InternalName != "Attachments")
    {
       newItem[field.InternalName] = sourceItem[field.InternalName];
    }
}

// ** Delete any existing attachments in the target item
for (int i = newItem.Attachments.Count; i > 0; i-- )
{
    newItem.Attachments.Delete(newItem.Attachments[i-1]);
}

// ** Copy any attachments
foreach (string fileName in sourceItem.Attachments)
{
    SPFile file = sourceItem.ParentList.ParentWeb.GetFile(sourceItem.Attachments.UrlPrefix + 
                                                          fileName);
    byte[] imageData = file.OpenBinary();
    newItem.Attachments.Add(fileName, imageData);
}

// ** Remember where the original was copied from so we can update it in the future
newItem["_M_CopySource"] = sourceItem["FileRef"];

newItem.Update();