主题：打印出错

此主题相关图片如下：0)$c)7eby1xo6{62o0ks`)r.png

Dim doc As New PrintDoc
Doc.PageSetting.BottomMargin = 0
Doc.PageSetting.topMargin = 0
Doc.PageSetting.leftMargin = 0
Doc.PageSetting.rightMargin = 0
doc.PageSetting.Width = 40 '纸张宽度为100毫米
doc.PageSetting.Height = 30 '纸张高度为120毫米
Dim tbl As Table = Tables("县区_table2")
tbl.sort= "考试号"
For i As Integer = 0 To tbl.Rows.count-1
Dim r As Row = tbl.Rows(i)
    Dim rx As new prt.RenderText
rx.Style.Font = New Font("黑体", 10, FontStyle.Bold) '设置字体
    rx.text =Chr(10) & " 东兴区18生地结业考试" & Chr(10) & Chr(10) & "  考场:" & trim(r("考试号")).Substring(4,3)  &  "   座位:" & trim(r("考试号")).Substring(7,2)  & Chr(10) & "  考号:" & r("考试号") & Chr(10) & "  姓名:" & r("姓名") & Chr(10) & Chr(10) & "  考点:" & r("考点学校")
    doc.Body.Children.Add(rx)
    If i < tbl.Rows.count-1 Then
        rx.BreakAfter = prt.BreakEnum.Page
    End If
Next
doc.preview()

老师，上面代码出现有时打印一两张就出现上面图的错误提示，请问是什么原因，怎么办，谢谢