主题：连接表的时候提示 已添加了具有相同键的项

代码如下：这个是哪里出了问题

Dim jb1 As New SQLJoinTableBuilder("sc","物料")
jb1.C
jb1.AddTable("物料","生产商编号","代理商","_Identify")
jb1.AddCols("物料代码","分类","品名","规格","批准文号","执行标准","注册批件有效期","供应商名称","供应商地址","供应商级别","报告编号")
jb1.Build()
Dim dt1 As fxDataSource = jb1.BuildDataSource
'
Dim jb2 As New SQLJoinTableBuilder("dl","代理品种")
jb2.C
jb2.AddTable("代理品种","编号","代理商","_Identify")
jb2.AddCols("物料代码","名称","地址")
jb2.Build()
Dim dt2 As fxDataSource = jb2.BuildDataSource
'
dt1.Combine("物料代码",dt2,"物料代码")
dt1.Show("sc") '显示统计结果
'