ASP的对象复制学习—ASP实例教程

<%
Dim oConn,oRs
Set oConn = Server.CreateObject("ADODB.Connection")
Set ors = Server.CreateObject("ADODB.RecordSet")
oConn.open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("db1.mdb")
Session("conn") = oConn
ors.open "select * from t1",Session("conn"),1,1
Response.write(oRs(0))
ors.close
Set ors = Nothing
oConn.close
Set oConn = Nothing
%>
这是网上流传的把Connection对象保存在Seesion对象中的代码，注意其中的：Session("conn") = oConn，对象的复制就是这样子的吗？下边我们来验证一下：

<%
Dim oConn,oRs
Set oConn = Server.CreateObject("ADODB.Connection")
Set ors = Server.CreateObject("ADODB.RecordSet")
oConn.open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("db1.mdb")
Session("conn") = oConn
ors.open "select * from t1",Session("conn"),1,1
Response.write(Session("conn").ConnectionString)
ors.close
Set ors = Nothing
oConn.close
Set oConn = Nothing
%>
结果出错，提示"缺少对象: 'Session(...)'"！这说明对象并没有复制成功，那Session("conn")是什么类型的呢？我们用TypeName(Session("conn"))来测试下，结果为"String"！出于好奇，我们直接输出Session("conn")看看：

Provider=Microsoft.Jet.OLEDB.4.0;Password="";User ID=Admin;Data Source=E:\www\db1.mdb;Mode=Share Deny None;Extended Properties="";Jet OLEDB:System database="";Jet OLEDB:Registry Path="";Jet OLEDB:Database Password="";Jet OLEDB:Engine Type=5;Jet OLEDB:Database Locking Mode=1;Jet OLEDB:Global Partial Bulk Ops=2;Jet OLEDB:Global Bulk Transactions=1;Jet OLEDB:New Database Password="";Jet OLEDB:Create System Database=False;Jet OLEDB:Encrypt Database=False;Jet OLEDB:Don't Copy Locale on Compact=False;Jet OLEDB:Compact Without Replica Repair=False;Jet OLEDB:SFP=False
这不是Connection对象的ConnectionString属性值吗？Connection对象默认的属性为ConnectionString，执行Session("conn") = oConn时只是将Connection对象默认属性的值赋给Session("conn")。那为什么用在oRs.open "select * from t1",Session("conn"),1,1也能成功呢？查找资料得出RecordSet对象open方法的第二个参数可以为Connection对象，也可以是数据库连接信息的字符串！Ok了，那在上边例子中的oConn对象完全是多余的，直接用下边代码即可：

<%
Dim ors
Set ors = Server.CreateObject("ADODB.RecordSet")
Session("conn") = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("db1.mdb")
ors.open "select * from t1",Session("conn"),1,1
Response.write(oRs(0))
ors.close
Set ors = Nothing
%>
结果无错。好了，到现在为止还剩下一个问题没有解决：怎么才是正确的对象复制方法？还是用Set语句：

<%
Dim oConn,oRs
Set oConn = Server.CreateObject("ADODB.Connection")
Set ors = Server.CreateObject("ADODB.RecordSet")
oConn.open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("db1.mdb")
Set Session("conn") = oConn
ors.open "select * from t1",Session("conn"),1,1
    Response.write(Session("conn").ConnectionString)
    Response.write("<br/>")
    Response.write(TypeName(Session("conn")))
ors.close
Set ors = Nothing
oConn.close
Set oConn = Nothing
%>
这次能显示出ConnectionString属性的信息了，结果也显示Session("conn")为Connection对象！