主题：WebBrowser当打开过doc或docx文件后，再次打开别的文件会提示未将对象引用设置到对象的实例。附件提取失败,可能并不存在附件!

Dim zs1 As Integer = Tables(e.form.name & "_table2").Count

If zs1 >0 Then
    Dim wb As WinForm.WebBrowser = e.Form.Controls("WebBrowser1")

wb.Address=Nothing

    Dim tb As WinForm.TabControl = e.Form.Controls("TabControl1")

……