"未将对象引用设置到对象的实例"是什么意思？

Question

在下面这个语句中未将对象引用设置到对象的实例;
for each tr in ds.tables("info").rows可以说的清楚点吗？

Answer 1

这个要求你必须声明tr是一个DataRow
dim tr as datarow

Answer 2

下面是我的代码，在忙看一下，谢谢！
sub tree(lasttable as string)
lastbbs()
countanswer()
countquestion()
dim conn as OleDbconnection
conn=new OleDbconnection
conn.connectionstring="provider=microsoft.jet.OleDb.4.0;data source=" & server.mappath("../mdb/conn.mdb")
conn.open()
dim sqlstr as string
dim ds as new dataset()
dim da as OleDbDataAdapter
dim rowid as integer '定义记录号
dim content,img,aux,item as string 'html 元素的ID
dim tr as datarow
dim tablename as string '定义树的表名
response.write("<table border='1' cellsapacing='1' cellpadding='0' BorderColor='RoyalBlue' width='730'>")
'历遍当前表中的记录
for each tr in ds.tables(lasttable).rows
response.write("<tr>")
response.write("<td>")
response.write(tr.item("subjectname"))
response.write("</td>")
response.write("</tr>")
rowid=tr.item("subjectid")
'将当前记录的子节点生成一张表
tablename="table" & rowid
sqlstr="select * from subsubject"
sqlstr &="where subjectid=" & rowid
da=new OleDbDataAdapter(sqlstr,conn)
da.fill(ds,tablename)
if ds.tables(tablename).rows.count<>0 then
response.write("<tr>")
response.write("<td width=50>")
response.write("<p align='right'><img src='closedb.gif'></p>")
response.write("</td>")
response.write("<td width=255>")
response.write("<b>")
response.write(tr.item("subjectname")) 
response.write("<b><br>")
response.write(tr.item("discript"))
response.write("</td>")
response.write("<td width=20>")
response.write(tr.item("admin"))
response.write("</td>")
response.write("<td width=90>")
response.write(ds.tables("question").rows.item("thequestion")) 
response.write("</td>")
response.write("<td width=85>")
response.write(ds.tables("answer").rows.item("theanswer"))
response.write("</td>")
response.write("<td width=160>")
response.write("<b>")
response.write(ds.tables("lastquestion").rows.item("sender"))
response.write("</b><br>")
response.write(ds.tables("lastquestion").rows.item("title"))
response.write(ds.tables("lastquestion").rows.item("adddate"))
response.write("</td>")
response.write("<tr>")
'将递归深度加深
tree(tablename)
else
welcome.text="数据库出现故障"
end if
next
response.write("</table>")
end sub