在DropDownList中显示树

一．创建如下数据库

string sql = "select * from speciality";

 

 

二．代码如下

public partial class _Default : System.Web.UI.Page

{

    //把数据从oracle数据库里读入到：DataTable dt;

    DataTable dt = DaoSpeciality.GetDataTable(sql);

 

    //创建一个结构和 dt 一样的 DataTable; 

    DataTable newTable = new DataTable();

 

    protected void Page_Load(object sender, EventArgs e)

    {

        if (!Page.IsPostBack)

        {   

            DataColumn dc = new DataColumn("speciality_id", Type.GetType("System.String"));

            newTable.Columns.Add(dc);

 

            DataColumn dc2 = new DataColumn("name", Type.GetType("System.String"));

            newTable.Columns.Add(dc2);

 

            int levels = 1;

            FilterData("0", ref levels);

 

            this.DropDownList1.DataSource = newTable;

            DropDownList1.DataTextField = "name";

            DropDownList1.DataValueField = "speciality_id";

            this.DropDownList1.DataBind();

        }

    }

 

    //递归，把过滤出来的数据添加到新建的 newTable 里。  

    private void FilterData(string speID, ref int levels)

    {

        string s = string.Empty;

        for (int j = 1; j < levels; j++)

        {

            s = s + "　　";

        }

 

        levels += 1;

        int curlevels = levels;

 

        DataRow[] dataRow = dt.Select("parent_id='" + speID + "'");

        for (int i = 0; i < dataRow.Length; i++)

        {

            DataRow dr = newTable.NewRow();

            dr["speciality_id"] = dataRow[i]["speciality_id"].ToString();

            dr["name"] = s + dataRow[i]["name"].ToString();

 

            newTable.Rows.Add(dr);

            FilterData(dataRow[i]["speciality_id"].ToString(), ref levels);

            levels = curlevels;

        }

    }

}

 

三．备注

也可以将（一）中的sql语句改为

string sql = @"select * from speciality

                        start with parent_id=0 

                        connect by prior  speciality_id = parent_id";

这样递归查出的结果集直接是树形结构了，我个人认为使FilterData()的遍历次数减少了。

 

四．效果如下