Handle ListItem attachments via CSOM

Question

I'm able to add OR remove attachments to/from a ListItem:

Remove

foreach (Attachment a in emailItem.AttachmentFiles)
{
    a.DeleteObject();
}
emailItem.Update();
ctx.ExecuteQuery();

Add

foreach (AttachmentFile file in data.NewAttachments)
{
    var attInfo = new AttachmentCreationInformation();
    attInfo.FileName = "Name";
    attInfo.ContentStream = new MemoryStream(theBytes);
    emailItem.AttachmentFiles.Add(attInfo);
}
emailItem.Update();
ctx.ExecuteQuery();

But when I combine them I get a conflict error when ctx.ExecuteQuery(); is called:

foreach (Attachment a in emailItem.AttachmentFiles)
{
    a.DeleteObject();
}
emailItem.Update();

foreach (AttachmentFile file in data.NewAttachments)
{
    var attInfo = new AttachmentCreationInformation();
    attInfo.FileName = "Name";
    attInfo.ContentStream = new MemoryStream(theBytes);
    emailItem.AttachmentFiles.Add(attInfo);
}
emailItem.Update();
ctx.ExecuteQuery();

I also tried to remove the first call to emailItem.Update(); but get the same error. I know I could split the code in two parts by reloading the item, but it would be generate two versions of it since it would get saved twice...don't think it is a nice solution.

Does somebody have a hint?

Answer 1

Please use below code:

foreach (AttachmentFile file in data.NewAttachments)
{
    var attInfo = new AttachmentCreationInformation();
    attInfo.FileName = "Name";
    attInfo.ContentStream = new MemoryStream(theBytes);
    emailItem.AttachmentFiles.Add(attInfo);
}
emailItem.Update();

foreach (Attachment a in emailItem.AttachmentFiles)
{
    a.DeleteObject();
}
emailItem.Update();


ctx.ExecuteQuery();

Hope it works for you.

Answer 2

Thanks to @Samir Khimani for the help, however the deleting of the attachments does not always work since it modifies the current iteration. I edited a little bit his answer followings:

bool update = false;

int oldFiles = item.AttachmentFiles == null || item.AttachmentFiles.Count == 0 ? 0 : item.AttachmentFiles.Count;

if (myData.NewAttachments != null && myData.NewAttachments.Length > 0)
{
    foreach (AttachmentFile file in myData.NewAttachments)
    {
        var attInfo = new AttachmentCreationInformation();
        attInfo.FileName = file.Name;
        attInfo.ContentStream = new MemoryStream(theBytes);

        item.AttachmentFiles.Add(attInfo);
    }
    update = true;
}

if (myData.AttachmentsToRemove != null && myData.AttachmentsToRemove.Length > 0)
{
    for (int i = oldFiles-1; i >= 0; i--)
    {
        Attachment a = item.AttachmentFiles[i];
        if (myData.AttachmentsToRemove.Contains(a.FileName))
        {
            a.DeleteObject();
            update = true;
        }
    }
}

if (update)
{
    item.Update();
    ctx.ExecuteQuery();
}