rx.Text = "产品数目: " & Rows.Count
改为:
rx.Text = "产品数目: " & DataTables("产品").Compute("Sum(库存)", "关联列 = '" & tbl.Rows(i)("关联列") & "'")
或者:
Dim sum As integer = 0
For Each sr as row in rows
sum = sum + sr("库存")
next
rx.Text = "产品数目: " & sum