在前幾個章節所介紹的TreeView
([ASP.NET 2.0]SiteMapPath無法正確指到帶有QueryString的路徑、
[ASP.NET 2.0]SiteMapPath WebControl)
有個限制(至少我覺得是限制)，那就是只能使用XML的資料格式
但假如我們的資料是資料庫形式的資料該怎麼辦?
有兩個解決方法：一是自己寫程式，將節點加到TreeViewNode裡；一是另外寫個類似TreeViewNode的Class自己用
我是選第二個方法，這樣我就不用每次使用TreeView時，都要在寫那麼長一段程式碼了
先寫一個XmlTreeModel，程式碼如下：
[csharp]public class XmlTreeModel {
#region Private Variable
private int _indexid;
private int _parentid;
private string _title = string.Empty;
private System.Collections.Generic.List
private XmlTreeModel _parent = null;
private string _pathoftreeindex = string.Empty;
private string _pathoftitle = string.Empty;
private string _xmltag = string.Empty;
private string _pathseparator = “/”; // 搭配TreeView.PathSeparator使用
#endregion
#region public enum XmlTreeModelPathType {…}
public enum XmlTreeModelPathType {
PathOfTreeIndex = 0,
PathOfTitle = 1
}
#endregion
#region Public Property
public int IndexID { get { return _indexid; } }
public int ParentID { get { return _parentid; } }
public string Title { get { return _title; } }
public System.Collections.Generic.List
public XmlTreeModel Parent { get { return _parent; } }
public string XmlTagName { get { return _xmltag; } }
public string PathSeparator {
get { return _pathseparator; }
set { _pathseparator = value; }
}
#endregion
#region 多型 public XmlTreeModel()
#region public XmlTreeModel(int indexid, string title) {…}
public XmlTreeModel(int indexid, string title) {
_indexid = indexid;
_title = title;
_pathoftitle = title;
_pathoftreeindex = indexid.ToString();
_xmltag = _title.Replace(‘ ‘, ‘_’);
}
#endregion
#region public XmlTreeModel(int indexid, string title, string xmltagname) {…}
public XmlTreeModel(int indexid, string title, string xmltagname) {
_indexid = indexid;
_title = title;
_pathoftitle = title;
_pathoftreeindex = indexid.ToString();
_xmltag = xmltagname;
}
#endregion
#endregion
#region public XmlTreeModel AppendChild(XmlTreeModel item) {…}
public XmlTreeModel AppendChild(XmlTreeModel item) {
item._parent = this;
item._parentid = this._indexid;
item._pathseparator = this._pathseparator;
item._pathoftreeindex = this._pathoftreeindex + this._pathseparator + item._pathoftreeindex;
item._pathoftitle = this._pathoftitle + this._pathseparator + item._pathoftitle;
_childnodes.Add(item);
return item;
}
#endregion
#region 多型 public string ToXMLString()
#region public string ToXMLString() {…}
public string ToXMLString() {
return ToXMLString(false);
}
#endregion
#region public string ToXMLString(bool bInsCrLf) {…}
public string ToXMLString(bool bInsCrLf) {
string cr = (bInsCrLf) ? “\n” : “”;
string sXml = “< " + this._xmltag + " IndexID=\"" + this._indexid + "\" Title=\"" + this._title + "\"";
if (this._childnodes.Count == 0) {
sXml += " />” + cr;
} else {
sXml += “>” + cr;
foreach (XmlTreeModel xtm in this._childnodes) {
string nXml = xtm.ToXMLString(bInsCrLf);
sXml += nXml;
}
sXml += “” + cr;
}
return sXml;
}
#endregion
#endregion
#region public XmlTreeModel SearchNode(string treePath, XmlTreeModelPathType pt) {…}
public XmlTreeModel SearchNode(string treePath, XmlTreeModelPathType pt) {
string chkPath = string.Empty;
switch (pt) {
case XmlTreeModelPathType.PathOfTreeIndex:
chkPath = this._pathoftreeindex;
break;
case XmlTreeModelPathType.PathOfTitle:
chkPath=this._pathoftitle;
break;
default:
break;
}
if (chkPath == treePath)
return this;
foreach (XmlTreeModel xtm in _childnodes) {
XmlTreeModel node = xtm.SearchNode(treePath, pt);
if (node != null)
return node;
}
return null;
}
#endregion
}[/csharp]
在寫一個讀取資料庫的Class
[csharp]using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
public class QAManager {
XmlTreeModel Root;
public string XmlString { get { return Root.ToXMLString(); } }
public QAManager() { SetXmlTreeModel(); }
#region private void SetXmlTreeModel() {…}
private void SetXmlTreeModel() {
SqlConnection cn = new SqlConnection(ConfigurationManager.ConnectionStrings[“ConnectionString”].ConnectionString);
cn.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = cn;
cmd.CommandType = CommandType.Text;
cmd.CommandText = “Select * From TB_QAClasses Order By DataPath”;
SqlDataReader reader = cmd.ExecuteReader();
Root = new XmlTreeModel(0, “Q & A”, “Root”);
while (reader.Read()) {
string path = (string)reader[“DataPath”];
string parentPath = path.Substring(0, path.LastIndexOf(‘/’));
XmlTreeModel xtm = Root.SearchNode(parentPath, XmlTreeModel.XmlTreeModelPathType.PathOfTreeIndex);
if (xtm != null) {
xtm.AppendChild(new XmlTreeModel((int)reader[“ClassID”], (string)reader[“Title”], “Class”));
}
}
reader.Close();
cmd.Dispose();
cn.Close();
cn.Dispose();
}
#endregion
}[/csharp]
備註一點：我所展現的樹狀路徑是記錄在資料庫中，而不是用計算的，因為每次都要計算，太累而且會影響Server loading
我的Table Schema如下：
[sql]CREATE TABLE [dbo].[TB_QAClasses] (
[ClassID] [int] IDENTITY (1, 1) NOT NULL ,
[Title] [nvarchar] (32) NOT NULL ,
[DataPath] [varchar] (256) NOT NULL
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[TB_QAClasses] ADD
CONSTRAINT [DF_TB_QAClasses_ParentID] DEFAULT (‘0’) FOR [DataPath],
CONSTRAINT [PK_TB_QAClasses] PRIMARY KEY CLUSTERED
(
[ClassID]
) ON [PRIMARY]
GO[/sql]
[2005/08/01 15:53補充]
資料表內容如下…
| ClassID | Title | DataPath |
| 1 | 類別一 | 0/1 |
| 2 | 類別二 | 0/2 |
| 3 | 類別一之一 | 0/1/3 |
| 4 | 類別二之一 | 0/2/4 |
準備工作已經做完了… 現在要來在網頁裡利用TreeView來展現樹狀資料了
1. 先在網頁裡新增兩個元件XmlDataSource(更名為xds)以及TreeView(更名為tv)
2. 將以下程式段加入你的程式碼網頁中
[csharp]protected void Page_Load(object sender, EventArgs e) {
if (!IsPostBack) {
SetTreeView();
}
}
private void SetTreeView() {
xds.Data = new QAManager().XmlString; // 利用QAManager自資料庫中取回資料並轉成XML格式
xds.GetXmlDocument().LoadXml(xds.Data); // 利用XmlDataSource的GetXmlDocument()載入XML資料
tv.DataBindings.Clear();
TreeNodeBinding tnb = new TreeNodeBinding();// 設定TreeView的節點
tnb.TextField = “Title”; //
tnb.ValueField = “IndexID”; //
tnb.ToolTipField = “Title”; //
tv.DataBindings.Add(tnb); //
tv.DataSourceID = “xds”; // 指定TreeView的DataSourceID為xds
tv.DataBind(); // 執行Databind()
tv.ExpandAll(); // 展開樹狀目錄
}[/csharp]
好了~ 執行看看吧… 利用以上方法，我想… 利用TreeView來展現資料庫裡的樹狀資料再也不是件難事了… ^^
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