dropdownlist联动菜单

 数据加载

if(!IsPostBack)    
            ...{
                initdrop(1);
                initdrop(2);

            }

//droplistdown数据绑定

public void initdrop(int flag)
        ...{
            string CS=Application.Get("myConnectionString").ToString();
            string myQuery="";
            
            if(flag==1)myQuery= "SELECT * from province order by myorder ";

                if(flag==2)myQuery= "SELECT * from city order by myorder ";
            
            myConnection = new OleDbConnection(CS);
            // Open the connection.
            myConnection.Open();

            myCommand= new OleDbCommand(myQuery);
            // Assign the connection property.
            myCommand.Connection  = myConnection;
            objDataReader=myCommand.ExecuteReader();
                

            while(objDataReader.Read())
            ...{

                     if(flag==1)
                DropDownList1.Items.Add(new ListItem(objDataReader["title"].ToString(),objDataReader["friendlinks"].ToString()));

                    if(flag==2)

                     DropDownList2.Items.Add(new ListItem(objDataReader["title"].ToString(),objDataReader["friendlinks"].ToString()));
            }
        
            if(objDataReader!=null)objDataReader.Close();
            if(myConnection!=null)myConnection.Close();

        }

//DropDownList1改变触发DropDownList2

private void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
        ...{
        initdrop(2);            
        }