Public Sub AddTableColumn(ByVal MdbFileName As String, ByVal TableName As String, _
ByVal NewColumnName As String, ByVal NewColoumType As ColumnDataType) '现有的数据库中表格添加字段
Try
Dim cat As ADOX.CatalogClass = New ADOX.CatalogClass
Dim myConn As New ADODB.Connection
myConn.ConnectionString = strCnnDataBase(MdbFileName)
myConn.Open()
cat.ActiveConnection = myConn
'定义表
Dim TB As ADOX.Table = cat.Tables(TableName)
Dim col As New ADOX.ColumnClass
col.ParentCatalog = cat
col.Type = NewColoumType ‘这里如果为adChar{129}文本类型，居然不能创建
col.Name = NewColumnName
TB.Columns.Append(col)
myConn.Close()
MsgBox("新建字段成功！", MsgBoxStyle.Information, "提示：")
Catch ex As Exception
MsgBox(ex.Message, MsgBoxStyle.Information, "出错提示：")
End Try
End Sub
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请问是什么原因？

大神帮帮我！