如何取出ArrayList中的值

[DMPX]

public ArrayList Agent()
{
ArrayList al = new ArrayList();
using(SqlConnection myConn = new SqlConnection(strConn))
{
string sql ="SELECT COUNT(Os),Os FROM Count_Visitor GROUP BY Os";

myConn.Open();
SqlDataReader dr =myCmd.ExecuteReader();
while(dr.Read())
{
Visitor visitor = new Visitor();
visitor.Count =(int)dr[0];
visitor.OS =(string)dr["Os"];

al.Add(visitor);
}
return al;
}
}

要分别取出Count,OS里的值该如何取呢?
for(int i=0;i<al.Count;i++)
{
........
}

[zorou_fatal]

for(int i=0;i<al.Count;i++)
{
Response.Write( ((Visitor)al[i]).OS );
}

[vivianfdlpw]

for(int i=0;i<al.Count;i++)
{
Visitor v=al[i] as Visitor;
Response.Write("OS: "+v.OS+" Count:"+v.Count.ToString());
}

[暗石绿]

如：
Visitor v0 = (Visitor)al[0];
Visitor v1 = (Visitor)al[1];
...