效果圖: 

代碼: 

復制代碼代碼如下:

using System.Data; 
using System.Web.UI.WebControls; 
/// <summary> 
/// 根據DataTable生成下拉列表樹 
/// </summary> 
public class DropDownListHelp 
{ 
private string gridline; 
private DataTable dt; 
public DropDownListHelp() 
{ 
// 
//TODO: 在此處添加構造函數邏輯 
// 
} 
/// <summary> 
/// 根據Datatable生成樹形下拉菜單 
/// </summary> 
/// <param name="datatable"></param> 
/// <param name="parentKeyField">上級節點關鍵字段</param> 
/// <param name="parentKey">上級節點值</param> 
/// <param name="keyField">本節點關鍵字段</param> 
/// <param name="sortString">排序字符串</param> 
/// <param name="ddl">DownList</param> 
public void createDropDownTree(DataTable datatable, string parentKeyField, string parentKey, string keyField, string textField, string sortString, DropDownList ddl) 
{ 
dt = datatable; 
ddl.Items.Add(new ListItem("", "")); 
addChildItems(parentKeyField, parentKey, keyField, textField, sortString, ddl); 
} 
/// <summary> 
/// 遞歸生成樹節點 
/// </summary> 
/// <param name="parentKeyField">上級節點關鍵字段</param> 
/// <param name="parentKey">上級節點值</param> 
/// <param name="keyField">本節點關鍵字段</param> 
/// <param name="sortString">排序字符串</param> 
/// <param name="ddl">DownList控件</param> 
/// <returns></returns> 
private void addChildItems(string parentKeyField, string parentKey, string keyField, string textField, string sortString, DropDownList ddl) 
{ 
DataView dv = new DataView(dt, parentKeyField + "='" + parentKey + "'", sortString, DataViewRowState.CurrentRows); 
int a = dv.Count; 
if (dv.Count == 0) 
{ 
return; 
} 
for (int i = 0; i < a; i++) 
{ 
gridline = ""; 
dv.RowFilter = parentKeyField + "='" + parentKey + "'"; 
dv.Sort = sortString; 
getTreeLine(parentKeyField, dv[i][parentKeyField].ToString(), keyField, dv[i][keyField].ToString(), sortString); 
dv.RowFilter = parentKeyField + "='" + parentKey + "'"; 
dv.Sort = sortString; 
ddl.Items.Add(new ListItem(gridline + (i == a - 1 ? "┗" : "┣") + dv[i][textField].ToString(), dv[i][keyField].ToString())); 
addChildItems(parentKeyField, dv[i][keyField].ToString(), keyField, textField, sortString, ddl); 
} 
dv.Dispose(); 
} 
/// <summary> 
/// 回溯生成樹的連接線 
/// </summary> 
/// <param name="parentKeyField">上級節點關鍵字段</param> 
/// <param name="parentKey">上級節點值</param> 
/// <param name="keyField">本節點關鍵字段</param> 
/// <param name="nodeKey">本節點值</param> 
/// <param name="sortString">排序字符串</param> 
/// <returns></returns> 
private void getTreeLine(string parentKeyField, string parentKey, string keyField, string nodeKey, string sortString) 
{ 
//選擇父層節點 
DataView dv = new DataView(dt, keyField + "='" + parentKey + "'", sortString, DataViewRowState.CurrentRows); 
if (dv.Count > 0) 
{ 
//選擇父節點同級節點 
dv.RowFilter = parentKeyField + "='" + dv[0][parentKeyField].ToString() + "'"; 
dv.Sort = sortString; 
for (int j = 0; j < dv.Count; j++) 
{ 
if (dv[j][keyField].ToString() == parentKey) 
{ 
if (j == dv.Count - 1) 
{ 
gridline = "　" + gridline; 
} 
else 
{ 
gridline = "┃" + gridline; 
} 
} 
} 
getTreeLine(parentKeyField, dv[0][parentKeyField].ToString(), keyField, dv[0][keyField].ToString(), sortString); 
} 
dv.Dispose(); 
} 
} 

調用: 

復制代碼代碼如下:

DropDownListHelp ddlHelper = new DropDownListHelp(); 
ddlHelper.createDropDownTree(dt, "parentID", "1", "ID","Text", "Text asc", DropDownList1);