3.5 以上代码使用了 LocationCollection 集合类，使用泛型集合创建该类（同样位于 APP_Code 目录下）：

using System.Collections.Generic;  

 

public class LocationCollection:List<Location>  

{  

     

}  

3.6 在 APP_Code 目录下创建 DAO 类用于访问数据库，添加必要的命名空间引用：

using System;  

using System.Data;  

using System.Data.SqlClient;  

 

public class DAO  

{  

}  

3.7 编写 GetLocations 方法，返回所在地集合对象（请根据实际情况修改数据库连接字符串）：

public LocationCollection GetLocations()  

{  

    LocationCollection locs = new LocationCollection();  

 

    using (SqlConnection conn = new  

        SqlConnection("server=.;uid=sa;pwd=00000000;database=temp;"))  

    {  

        conn.Open();  

 

        SqlCommand cmd = new SqlCommand();  

        cmd.CommandText = "pr_GetLocations";  

        cmd.CommandType = CommandType.StoredProcedure;  

        cmd.Connection = conn;  

 

        SqlDataReader reader = cmd.ExecuteReader();  

                     

        int level = 0;  

        int oldlevel = 1;  

 

        LocationCollection container=new LocationCollection();  

        LocationCollection current = new LocationCollection();  

 

        while (reader.Read())  

        {  

            Location loc = GetLocationFromReader(reader, out level);  

 

            if (level == 0)  

            {  

                locs.Add(loc);  

                container.Add(loc);                   

            }  

            else  

            {  

                if (oldlevel != level)  

                {  

                    container.Clear();  

 

                    foreach (Location l in current)  

                        container.Add(l);  

 

                    current.Clear();  

                    oldlevel = level;  

                }  

 

                current.Add(loc);  

 

                CreateLocation(container, loc);  

            }                 

        }  

    }  

 

    return locs;  

}  

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