dataobj.cs

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namespace TwoLayer
{
using System;
using System.Data;
using System.Data.SqlClient;

  public class DataObj 
  {
    private String _connStr;

    //无参数的构造函数
    public DataObj() 
    {
      _connStr = null;
    }

    //含参数的构造函数，参数为ConnetionString
    public DataObj(String connStr) 
    {
      _connStr = connStr;
    }

    //公用属性ConnectionString（连接参数）
    public string ConnectionString 
    {
      get 
      {
        return _connStr;
      }
      set 
      {
        _connStr = value;
      }
    }

    //方法GetCity用于返回包含不同城市名的DataView类型的值
    public DataView GetCity() 
    {
      SqlConnection myConnection = new SqlConnection(_connStr);
      //查询所有在Employees中不同的城市名
      SqlDataAdapter myCommand = new SqlDataAdapter("select distinct City from Employees", myConnection);

      DataSet ds = new DataSet();
      myCommand.Fill(ds, "Employees");

      return ds.Tables["Employees"].DefaultView;
    }

    //方法GetEmployeesForCity用于返回CityValue城市的所有员工的列表
    public DataView GetEmployeesForCity(String CityValue) 
    {
      SqlConnection myConnection = new SqlConnection(_connStr);
      string  cmdstr="select * from Employees where City='" + CityValue + "'";
      SqlDataAdapter myCommand = new SqlDataAdapter(cmdstr, myConnection);

      DataSet ds = new DataSet();
      myCommand.Fill(ds, "Details");

      return ds.Tables["Details"].DefaultView;
    }
  }

}