主题：请教循环遍历结构问题

For each dr dataRow in DataTables("xxx")

   '循环读取

next

DataTables("xxx").DataRows.Clear '全部删除

没有看懂，避免出错的方法：

Public Function GenProductBom(ByVal rootid As Integer,ByVal goid As Integer,ByVal formatstr As String,ByVal NeedTotal As Double,ByVal onetotal As Double) As Boolean
Dim cmd As New SQLCommand
Dim dt As DataTable
cmd.CommandText ="Select goid,singletotal,comgoid,sf_nonstock,ord From {cp_singlebom} Inner JOIN {product} ON {product}.[_Identify] = {cp_singlebom}.[goid]  where {cp_singlebom}.[goid]=" & Cstr(goid)
dt = cmd.ExecuteReader()
Dim r2 As Row = Tables("bomdata").AddNew()
r2("goid") = rootid
r2("nodegoid") = goid
r2("sortkey") = Formatstr
r2("total") = NeedTotal
r2("Singletotal") = onetotal

If dt.DataRows.Count > 0 Then
    For Each dr As DataRow In dt.DataRows
        Dim r As Row = Tables("tempbom").AddNew()
        r("goid")=dr("comgoid")
        r("singletotal") = dr("singletotal")
        r("total") = dr("singletotal") * NeedTotal
        r("sortkey")= Formatstr + "/" + Format(dr("ord"),"000")
    Next
End If

Dim cnt As Integer = DataTables("tempbom").DataRows.Count -1

Do While DataTables("tempbom").DataRows.Count > 0
    Dim r  As DataRow = DataTables("tempbom").DataRows(0)
    Dim dt1 As DataTable
    Dim cmd1 As New SQLCommand
    Dim curgoid As Integer
    Dim fstr As String
    Dim curSingletotal As Double = r("singletotal")
    Dim curTotal As Double = r("total")
    curgoid = r("goid")
    fstr = r("sortkey")
    'MessageBox.Show(cstr(curgoid),"info",MessageBoxButtons.OK,MessageBoxIcon.Information)
    r.Delete
    cmd1.CommandText = "Select goid,singletotal,comgoid,sf_nonstock,ord From {cp_singlebom} Inner JOIN {product} ON {product}.[_Identify] = {cp_singlebom}.[goid]  where {cp_singlebom}.[goid]=" & CSTR(curgoid)
    dt1 = cmd1.ExecuteReader()
   
    If dt1.DataRows.Count > 0 Then
        GenProductBom(rootid,curgoid,fstr,curtotal,cursingletotal)
    Else
        '追加到数据表中
        Dim r1 As Row = Tables("bomdata").AddNew()
        r1("goid") = rootid
        r1("nodegoid") = curgoid
        r1("sortkey") = fstr
        r1("singletotal")=cursingletotal
        'r1("sf_summy")= dr("sf_nonstock")
        r1("total")= curtotal
    End If
Loop
Return True
End Function