主题：[已解决！谢谢]身份证正则表达式该怎么改?

Dim str As String
Dim dlg As New OpenFileDialog '定义一个新的OpenFileDialog
dlg.Filter= "txt文件|*.txt" '设置筛选器
If dlg.ShowDialog = DialogResult.Ok Then '如果用户单击了确定按钮
    str= FileSys.ReadAllText(dlg.FileName, Encoding.Default)
End If

Dim mc = System.Text.RegularExpressions.Regex.Matches(str, "(?<=<td colspan=""2"">)[0-9]{18}")
Dim md = System.Text.RegularExpressions.Regex.Matches(str, "(?<=<td>)[0-9]{12}")
If mc.count > 0 Then
    For i As Integer = 1 To mc.count
        Dim dr As DataRow =DataTables("Train_info").find("[Class_ID] = '" & Vars("ClassId")& "'  And [ID_CARD] = '" & mc(i-1).value & "'   ")
        If dr IsNot Nothing Then
            dr("examnum") = md(i-1).value
           
        End If
       
    Next

其中带X的身份证都找不出来，正则该怎么修改呢？