主题：录入多行重复材料资料，如何出现警告

If e.Form.Controls("ComboBox1").Value = Nothing Then
    MessageBox.Show("请选择供应商")
    Return
End If

For Each r As Row In Tables("临时材料表").rows
    For Each c As Col In Tables("临时材料表").cols
        If r.IsNull(c.name) Then
            MessageBox.Show(r.index+1 & "行 " & c.name & " 列为空")
            Return
        End If
    Next
Next

Dim Cols1() As  String = {"产品名称","型号规格","单位","单价"}
Dim Cols2() As  String = {"产品名称","型号规格","单位","单价"}
Dim idxs As String = "-1,"
For Each dr1 As DataRow In DataTables("临时材料表").Select("")
    Dim dr2 As DataRow = DataTables("材料表").find("供应商 = '" & e.Form.Controls("ComboBox1").text & "' and 产品名称 = '" & dr1("产品名称") & "' and 型号规格 = '" & dr1("型号规格") & "'")
    If dr2 Is Nothing Then
        dr2 = DataTables("材料表").AddNew()
        dr2("供应商")=e.Form.Controls("ComboBox1").text
        For i As Integer = 0 To Cols1.Length-1
            dr2(Cols2(i))=dr1(Cols1(i))
        Next
        idxs &= dr1("_Identify") & ","
    End If
Next
DataTables("临时材料表").DeleteFor("_Identify in (" & idxs.trim(",") & ")")