DataSet ds =
ds.Tables.Add(dt1);
ds.Tables.Add(dt2);
ds.Relations.Add("NestThem",ds.Tables[0].Columns["CASSITEMNMBR"], ds.Tables[1].Columns["CASS_ITEMNBR"]);
public
{
DataRowView drv = e.Item.DataItem
Repeater innerRep = e.Item.FindControl("NestedRepeater")
innerRep.DataSource = drv.CreateChildView("NestThem");
innerRep.DataBind();
}