主题：[求助]放到命令窗口报错，哪句类型转换出错？

'注意:本复制过程不能取取表达式列,当然不能复制表达式列
'查询各列再新建
'1.1建来源表建立参数空间
Dim DataTabSelf As DataTable = DataTables("表A")
    If DataTables.Contains("Data_" & DataTabSelf.Name) = True Then '如果表已经加载
        Return Nothing '则退出函数
    End If

'1.2为取来源表建立第二批空间
 
    Dim SumRow As Integer = DataTabSelf.DataRows.Count
    Dim SumCol As Integer = DataTabSelf.DataCols.Count
    Dim TotalCell As Integer = DataTabSelf.DataRows.Count*DataTabSelf.DataCols.Count
    Dim BaseTabName As String = "Data_" & DataTabSelf.Name
    Dim RowEmpty As Integer
    RowEmpty = 4
    Dim RowCap(RowEmpty)  As String      
    If TotalCell > 5240  Then '如果数据过多,接近5250个上限
        MessageBox.Show("数据过多,接近5250个上限,退出")
    Return Nothing '则退出函数
    End If
'1.3为目标表建立空间并复制表列,仅复制结构,不复制数据
    Dim Builder As New ADOXBuilder
    Dim tbl As ADOXTable
    Dim i As Integer = 0
    Dim j As Integer = 0
    Dim LeiXing As Integer
    Dim DcName As String
    Dim DcCaption As String
    Dim DcDatatype As Integer
    Dim DcMaxlength As String

    Builder.Open()
    tbl = Builder.NewTable( "Data_" & DataTabSelf.Name)
    With tbl
          .AddColumn( "RowColLable" ,ADOXType.String ,16)
          .AddColumn( "RowColContent" ,ADOXType.String ,200)
            For Each dc As DataCol In DataTabSelf.DataCols
               DcName = dc.Name
               DcCaption =dc.Caption
               DcDatatype =dc.Datatype.tostring()
               DcMaxlength =dc.MaxLength
             .AddColumn( DcName ,DcDatatype ,DcMaxlength)
            Next
    End With
   
    Builder.AddTable(tbl) '增加表
    Builder.Close()

    If DataTables.Contains("Data_" & DataTabSelf.Name) = False Then '如果新表没有加载
        DataTables.Load("Data_" & DataTabSelf.Name) '加载新表
    End If