主题：datacolchanged报错

If e.DataCol.name = "科目代码" Then

    If e.DataRow.IsNull("科目代码") Then

        e.DataRow("会计科目_一级科目") = ""

        e.DataRow("会计科目_明细科目") = ""

    Else

        Dim str As String = e.DataRow("科目代码")

        If str.Length = 4 Then

            Dim dr As DataRow = DataTables("会计科目").find("科目代码 = '"& e.datarow("科目代码") & "'")

            e.DataRow("会计科目_一级科目") = dr("科目名称")

            e.DataRow("会计科目_明细科目") = ""

        Else

            Dim str1 As String = str.SubString(0,4)

            Dim dr1 As DataRow = DataTables("会计科目").find("科目代码 = '"& str1 & "'")

            e.DataRow("会计科目_一级科目") = dr1("科目名称")

            Dim dr2 As DataRow = DataTables("会计科目").find("科目代码 = '"& str & "'")

            e.DataRow("会计科目_明细科目") = dr2("科目名称")

        End If

    End If

End If

在窗口的按钮中写了如下代码:

Dim t As Table =  Tables("凭证.凭证明细")

t.AddNew(2)

t.Rows(0)("科目代码") = "1211001"

t.Rows(1)("科目代码") = "217100101"

Dim str As String = Forms("凭证录入").Controls("lb凭证ID").text

Dim dt As DataTable = Tables("进项piao_table1").DataTable

For Each id As String In dt.GetValues("科目代码","凭证ID = '"& str & "'")

    Dim r As Row = Tables("凭证.凭证明细").AddNew()

    r("科目代码") = id

    r("贷方金额") = dt.Compute("sum(fa piao金额)","科目代码= '"& id & "'and 凭证ID = '"& str & "'")

    Dim dr As DataRow = dt.find("科目代码= '"& id & "'and 凭证ID = '"& str & "'")

    r("摘要") = dr("销方名称").Substring(0,6) & "购:" & dr("fa piao摘要")

Next

t.Rows(0)("借方金额") = dt.Compute("sum(金额)","凭证ID = '"& str & "'")

t.Rows(1)("借方金额") = dt.Compute("sum(税额)","凭证ID = '"& str & "'")

Dim s As String = dt.GetComboListString("fa piao摘要","凭证ID = '"& str & "'")

s = s.Replace("|"," ")

t.Rows(0)("摘要") = "购:" & s 

t.Rows(1)("摘要") = "进项税:" & s