Attach document in custom list item using Client Object Model?

using (ClientContext context = new ClientContext("http://SharepointURL/"))
{
    try
    {


        Web web = context.Web;

        FileCreationInformation newFile = new FileCreationInformation();
        newFile.Content = System.IO.File.ReadAllBytes(@"C:\test.txt");
        newFile.Url = "test.txt";

        List docs = web.Lists.GetByTitle("CustomList");
    ListItem item = docs.GetItemById(ID);

    var attInfo = new AttachmentCreationInformation();
    attInfo.FileName = mFile.Name;
    attInfo.ContentStream = new MemoryStream(System.IO.File.ReadAllBytes("streamFile"));

    Attachment att = item.AttachmentFiles.Add(attInfo); //Add to File

    context.Load(att);
    context.ExecuteQuery();
    Console.WriteLine("done");


    }
    catch (Exception ex)
    {
        throw ex;
    }
}

Hope this code helps you to attach file to list item.