通过递归方法 将DataTable中的树状数据信息 按树状格式显示在DropDownList中

DataTable中的数据：
TypeID , TypeName , ParentTypeID
1 类别A 0
2 类别B 0
3 子类别B1 2
4 子类别A1 1
5 孙类别A11 4

DropDownList的显示效果：
类别A
|--子类别A1
|----孙类别A11
类别B
|--子类别B1

Code
#region绑定
privatevoidfn_Bind_DropDownList()
{
DataSetds;

//数据库操作取出相应的ds
//ds=bll_Type.SelectAllTypeForChoose();

this.ddl_Type.Items.Clear();
if(ds!=null&&ds.Tables.Count>0&&ds.Tables[0].Rows.Count>0)
{
DataTabledtPara=ds.Tables[0];
DataTabledtTree=newDataTable();
dtTree=dtPara.Clone();
fn_ChangeToTree(refdtTree,dtPara,0,"0");//从顶级开始递归遍历

this.ddl_Type.DataSource=dtTree;
this.ddl_Type.DataTextField=dtTree.Columns[1].ToString();
this.ddl_Type.DataValueField=dtTree.Columns[0].ToString();
this.ddl_Type.DataBind();
}
this.ddl_Type.Items.Insert(0,newListItem("","0"));
}
#endregion

#region将类别DataTable信息整理成树状显示
privatevoidfn_ChangeToTree(refDataTabledtTree,DataTabledtPara,intintLevel,stringstrParentTypeID)
{
intLevel++;
stringstrLeftPre="";//处理每个级别的前缀内容显示
if(intLevel>1)
{
strLeftPre="|"+strLeftPre.PadLeft(intLevel*2,'-');
}

DataTabledt1=newDataTable();//当前类别
dt1=dtPara.Clone();
DataTabledt2=newDataTable();//下一级
dt2=dtPara.Clone();

for(inti=0;i<dtPara.Rows.Count;i++)
{
DataRowdr=dtPara.Rows[i];
stringstrRowParentTypeID=dr["ParentTypeID"].ToString();
if(strRowParentTypeID==strParentTypeID)
{
dt1.Rows.Add(dr.ItemArray);
}
else
{
dt2.Rows.Add(dr.ItemArray);
}
}

for(intj=0;j<dt1.Rows.Count;j++)
{
DataRowdr=dt1.Rows[j];

dr["TypeName"]=strLeftPre+dr["TypeName"].ToString();
dtTree.Rows.Add(dr.ItemArray);
stringstrRowParentTypeID=dr["TypeID"].ToString();
fn_ChangeToTree(refdtTree,dt2,intLevel,strRowParentTypeID);//递归
}
}
#endregion