Delete File From Library

public void DeleteFileFormLibrary(string siteUrl, string webName, string listName, string subfolder, string attachmentFileName)
{
    using (ClientContext clientContext = new ClientContext(siteUrl))
    {
        string attachmentPath = string.Empty;
        if (string.IsNullOrEmpty(subfolder))
        {
            attachmentPath = string.Format("/{0}/{1}/{2}", webName, listName, Path.GetFileName(attachmentFileName));
        }
        else
        {
            attachmentPath = string.Format("/{0}/{1}/{2}/{3}", webName, listName, subfolder, Path.GetFileName(attachmentFileName));
        }
        var file = clientContext.Web.GetFileByServerRelativeUrl(attachmentPath);
        file.DeleteObject();
        clientContext.ExecuteQuery();
    }
}