/// <summary>
/// 读一个变量
/// </summary>
/// <param name="tag"></param>
/// <returns></returns>
public TagItem Read(TagItem tag)
{
DataValue value = uAClient.ReadValue(tag.GetNodeId());
tag.Value = value.Value;
tag.Quality = value.StatusCode.ToString();
tag.Timestamp = value.SourceTimestamp;
return(tag);
}