I don't think many of u have experience with DataTable.Load or DataTable.Merge, so here I take time to write it down for future check and records.
The MSDN document has a good sample and explanation about Load method: http://msdn.microsoft.com/en-us/library/4e06d41f.aspx
Too long for a lazy man to read, hum? Here is the sample running result, which I think can clarify the things up:
One item has a historical original value and a current value.
LoadOption.OverwriteChanges option means to overwrite both//全部覆盖
LoadOption.PreserveChanges option means to overwrite unchanged current value and original value//覆盖未改变的最新值和所有原始值
LoadOption.Upsert option means to overwrite undeleted current value and keep original value//覆盖未删除的最新值，保留原始值
I guess Load method internally calls Merge method.
If you want to append a DataTable to another, you'd use DataTable.Rows.Add method, instead.