SharePoint 2010 - Client Object Model - Add attachment to ListItem

Question

I have a SharePoint List to which I\'m adding new ListItems using the Client Object Model. Adding ListItems is not a problem and works great.

Now I want to add att

Answer 1

HTML:

Event in code behind :

protected void UploadMultipleFiles(object sender, EventArgs e)
{
    Common.UploadDocuments(Common.getContext(new Uri(Request.QueryString["SPHostUrl"]),
    Request.LogonUserIdentity), FileUpload1.PostedFiles, new CustomerRequirement(), 5);
}

public static List UploadDocuments(ClientContext ctx,IList selectedFiles, T reqObj, int itemID)
{
    List existingFiles = null;
    List processedFiles = null;
    List unProcessedFiles = null;
    ListItem item = null;
    FileStream sr = null;
    AttachmentCollection attachments = null;
    byte[] contents = null;
    try
    {
        existingFiles = new List();
        processedFiles = new List();
        unProcessedFiles = new List();
        //Get the existing item
        item = ctx.Web.Lists.GetByTitle(typeof(T).Name).GetItemById(itemID);
        //get the Existing attached attachments
        attachments = item.AttachmentFiles;
        ctx.Load(attachments);
        ctx.ExecuteQuery();
        //adding into the new List
        foreach (Attachment att in attachments)
            existingFiles.Add(att);
        //For each Files which user has selected
        foreach (HttpPostedFile postedFile in selectedFiles)
        {
            string fileName = Path.GetFileName(postedFile.FileName);
            //If selected file not exist in existing item attachment
            if (!existingFiles.Any(x => x.FileName == fileName))
            {
                //Added to Process List
                processedFiles.Add(postedFile.FileName);
            }
            else
                unProcessedFiles.Add(fileName);
        }
        //Foreach process item add it as an attachment
        foreach (string path in processedFiles)
        {
            sr = new FileStream(path, FileMode.Open);
            contents = new byte[sr.Length];
            sr.Read(contents, 0, (int)sr.Length);
            var attInfo = new AttachmentCreationInformation();
            attInfo.FileName = Path.GetFileName(path);
            attInfo.ContentStream = sr;
            item.AttachmentFiles.Add(attInfo);
            item.Update();
        }
        ctx.ExecuteQuery();
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        existingFiles = null;
        processedFiles = null;
        item = null;
        sr = null;
        attachments = null;
        contents = null;
        ctx = null;

    }
    return unProcessedFiles;
}