以下代码是论坛里的 导入EXCEL表数据，关键字段（身份证号）数据重复时导入

是进行数据覆盖的，请问老师如果不覆盖，而是选择跳过 该怎么写？

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Dim dt As DataTable = DataTables("认证报名表")
Dim Result As DialogResult
Result = MessageBox.Show("确定要导入吗?", "提示", MessageBoxButtons.YesNo, MessageBoxIcon.Question)
If Result = DialogResult.Yes Then
    Dim dlg As New OpenFileDialog
    dlg.Filter = "Excel文件|*.xls"
    dlg.MultiSelect = True \'允许选择多个文件
    If dlg.ShowDialog =DialogResult.OK Then
        Dim Book As New XLS.Book(dlg.FileName)
        Dim Sheet As XLS.Sheet = Book.Sheets("认证报名表")
        dt.ResumeRedraw()
        dt.StopRedraw()
        \'systemready = False
        Dim nms As New Dictionary(Of String, Integer)
        Dim dic As new Dictionary(Of DataRow, Integer)
        Dim ls As new List(Of Integer)
        For c As Integer = 0 To sheet.Cols.Count - 1
            If  dt.DataCols.Contains(sheet(0,c).Text.replace(" ", "")) Then
                nms.Add(sheet(0,c).Text.replace(" ", ""), c)
            End If
        Next
        For n As Integer = 1 To Sheet.Rows.Count -1
            Dim sfzhm As String = sheet(n,nms("身份证号码")).Text
            If sfzhm = "" Then Continue For
            Dim dr As DataRow = dt.Find("身份证号码 = \'" & sfzhm & "\'")
            If dr Is Nothing Then
                ls.add(n)
            Else
                dic.Add(dr, n)
            End If
        Next
        For Each key As DataRow In dic.Keys
            For Each m As String In nms.keys
                If dt.DataCols(m).IsBoolean Then
                    If Sheet(dic(key),nms(m)).Text = "" OrElse Sheet(dic(key),nms(m)).Text = "False" OrElse Sheet(dic(key),nms(m)).Value = 0 Then
                        key(m) = False
                    Else
                        key(m) = True
                    End If
                Else If dt.DataCols(m).Expression > "" Then
                    \'表达式列
                Else If dt.DataCols(m).IsNumeric Then
                    key(m) = val(Sheet(dic(key),nms(m)).Value)
                Else If dt.DataCols(m).IsDate Then
                    Dim d As Date
                    If Date.TryParse(Sheet(dic(key),nms(m)).Value, d)
                        key(m) = d
                    End If
                   
                Else
                    key(m) = Sheet(dic(key),nms(m)).Value
                End If
            Next
        Next
        For Each l As Integer In ls
            Dim ndr As DataRow = dt.AddNew
            For Each m As String In nms.keys
                If dt.DataCols(m).IsBoolean Then
                    If Sheet(l,nms(m)).Text = "" OrElse Sheet(l,nms(m)).Text = "False" OrElse Sheet(l,nms(m)).Value = 0 Then
                        ndr (m) = False
                    Else
                        ndr (m) = True
                    End If
                Else If dt.DataCols(m).Expression > "" Then
                    \'表达式列
                Else If dt.DataCols(m).IsNumeric Then
                    ndr (m) = val(Sheet(l,nms(m)).Value)
                Else If dt.DataCols(m).IsDate Then
                    Dim d As Date
                    If Date.TryParse(Sheet(l,nms(m)).Value, d)
                        ndr (m) = d
                    End If
                Else
                   
                    ndr (m) = Sheet(l,nms(m)).Value
                End If
            Next
        Next
        dt.ResumeRedraw()
        \'systemready = True
    End If
End If

改成

            If dr Is Nothing Then
                ls.add(n)
            Else
                \'dic.Add(dr, n)
            End If