DropDownList无限级分类(灵活控制显示形式)

protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
BindDrpClass();
}
}

/// <summary>
/// 绑定顶级分类
/// </summary>
private void BindDrpClass()
{
DataTable dt = GetClassList("").Tables[0];
ddlClass.Items.Clear();
ddlClass.Items.Add(new ListItem("添加根栏目", "0"));
DataRow[] drs = dt.Select("ParentID= " + 0);

foreach (DataRow dr in drs)
{
string classid = dr["ClassID"].ToString();
string classname = dr["ClassName"].ToString();
//顶级分类显示形式
classname = "╋" + classname;

ddlClass.Items.Add(new ListItem(classname, classid));
int sonparentid = int.Parse(classid);
string blank = "├";
//递归子分类方法
BindDrpNode(sonparentid, dt, blank);
}
ddlClass.DataBind();
}

/// <summary>
/// 绑定子分类
/// </summary>
/// <param name="parentid"></param>
/// <param name="dt"></param>
/// <param name="blank"></param>
private void BindDrpNode(int parentid, DataTable dt, string blank)
{
DataRow[] drs = dt.Select("ParentID= " + parentid);

foreach (DataRow dr in drs)
{
string classid = dr["ClassID"].ToString();
string classname = dr["ClassName"].ToString();

classname = blank + classname;
ddlClass.Items.Add(new ListItem(classname, classid));

int sonparentid = int.Parse(classid);
string blank2 = blank + "─";

BindDrpNode(sonparentid, dt, blank2);
}
}

/// <summary>
/// 数据访问
/// </summary>
/// <param name="strWhere">SQL条件</param>
/// <returns></returns>
public DataSet GetClassList(string strWhere)
{
StringBuilder strSql = new StringBuilder();
strSql.Append("select * from tb_Class ");
if (strWhere.Trim() != "")
{
strSql.Append(" where " + strWhere);
}
return DAL.SqlHelper.ExecuteDataset(DAL.SqlHelper.ConnString, CommandType.Text, strSql.ToString());
}