C# 从数据库填充 TreeView
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Populate TreeView from DataBase
提问by Tarik
I have a database table (named Topics) which includes these fields :
我有一个数据库表（名为 Topics），其中包括以下字段：
- topicId
- name
- parentId
- 主题ID
- 姓名
- 父ID
and by using them I wanna populate a TreeView in c#. How can I do that ?
通过使用它们，我想在 c# 中填充一个 TreeView。我怎样才能做到这一点 ？
Thanks in advance...
提前致谢...
采纳答案by Bob
It will probably be something like this. Give some more detail as to what exactly you want to do if you need more.
它可能是这样的。如果您需要更多，请详细说明您到底想做什么。
//In Page load
foreach (DataRow row in topics.Rows)
{
TreeNode node = new TreeNode(dr["name"], dr["topicId"])
node.PopulateOnDemand = true;
TreeView1.Nodes.Add(node);
}
///
protected void PopulateNode(Object sender, TreeNodeEventArgs e)
{
string topicId = e.Node.Value;
//select from topic where parentId = topicId.
foreach (DataRow row in topics.Rows)
{
TreeNode node = new TreeNode(dr["name"], dr["topicId"])
node.PopulateOnDemand = true;
e.Node.ChildNodes.Add(node);
}
}
回答by Brody
Not quite.
不完全的。
Trees are usually handled best by not loading everything you can at once. So you need to get the root node (or topic) which has no parentIDs. Then add them to the trees root node and then for each node you add you need to get its children.
树木通常最好不要一次性加载所有内容。因此，您需要获取没有 parentID 的根节点（或主题）。然后将它们添加到树的根节点，然后对于您添加的每个节点，您需要获取其子节点。
foreach (DataRow row in topicsWithOutParents.Rows)
{
TreeNode node = New TreeNode(... whatever);
DataSet childNodes = GetRowsWhereParentIDEquals(row["topicId"]);
foreach (DataRow child in childNodes.Rows)
{
Treenode childNode = new TreeNode(..Whatever);
node.Nodes.add(childNode);
}
Tree.Nodes.Add(node);
}
回答by Brij
When there are no Large Amounts of Data then it is not good to connect database, fetch data and add to treeview node again and again for child/sub nodes. It can be done in single attempt. See following sample:
http://urenjoy.blogspot.com/2009/08/display-hierarchical-data-with-treeview.html
当没有大量数据时，对于子/子节点，连接数据库，获取数据并一次又一次地添加到树视图节点是不好的。它可以在一次尝试中完成。请参阅以下示例：http:
//urenjoy.blogspot.com/2009/08/display-hierarchical-data-with-treeview.html
回答by MAK
this code runs perfectly for me, check it out i think it will help you :)
这段代码对我来说运行得很好，检查一下我认为它会帮助你:)
;
;
protected void Page_Load(object sender, EventArgs e)
{
DataSet ds = RunQuery("Select topicid,name from Topics where Parent_ID IS NULL");
for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
{
TreeNode root = new TreeNode(ds.Tables[0].Rows[i][1].ToString(),ds.Tables[0].Rows[i][0].ToString());
root.SelectAction = TreeNodeSelectAction.Expand;
CreateNode(root);
TreeView1.Nodes.Add(root);
}
}
void CreateNode(TreeNode node)
{
DataSet ds = RunQuery("Select topicid, name from Category where Parent_ID =" + node.Value);
if (ds.Tables[0].Rows.Count == 0)
{
return;
}
for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
{
TreeNode tnode = new TreeNode(ds.Tables[0].Rows[i][1].ToString(), ds.Tables[0].Rows[i][0].ToString());
tnode.SelectAction = TreeNodeSelectAction.Expand;
node.ChildNodes.Add(tnode);
CreateNode(tnode);
}
}
DataSet RunQuery(String Query)
{
DataSet ds = new DataSet();
String connStr = "???";//write your connection string here;
using (SqlConnection conn = new SqlConnection(connStr))
{
SqlCommand objCommand = new SqlCommand(Query, conn);
SqlDataAdapter da = new SqlDataAdapter(objCommand);
da.Fill(ds);
da.Dispose();
}
return ds;
}
回答by duc14s
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
PopulateRootLevel();
}
private void PopulateRootLevel()
{
SqlConnection objConn = new SqlConnection(connStr);
SqlCommand objCommand = new SqlCommand(@"select FoodCategoryID,FoodCategoryName,(select count(*) FROM FoodCategories WHERE ParentID=c.FoodCategoryID) childnodecount FROM FoodCategories c where ParentID IS NULL", objConn);
SqlDataAdapter da = new SqlDataAdapter(objCommand);
DataTable dt = new DataTable();
da.Fill(dt);
PopulateNodes(dt, TreeView2.Nodes);
}
private void PopulateSubLevel(int parentid, TreeNode parentNode)
{
SqlConnection objConn = new SqlConnection(connStr);
SqlCommand objCommand = new SqlCommand(@"select FoodCategoryID,FoodCategoryName,(select count(*) FROM FoodCategories WHERE ParentID=sc.FoodCategoryID) childnodecount FROM FoodCategories sc where ParentID=@parentID", objConn);
objCommand.Parameters.Add("@parentID", SqlDbType.Int).Value = parentid;
SqlDataAdapter da = new SqlDataAdapter(objCommand);
DataTable dt = new DataTable();
da.Fill(dt);
PopulateNodes(dt, parentNode.ChildNodes);
}
protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
{
PopulateSubLevel(Int32.Parse(e.Node.Value), e.Node);
}
private void PopulateNodes(DataTable dt, TreeNodeCollection nodes)
{
foreach (DataRow dr in dt.Rows)
{
TreeNode tn = new TreeNode();
tn.Text = dr["FoodCategoryName"].ToString();
tn.Value = dr["FoodCategoryID"].ToString();
nodes.Add(tn);
//If node has child nodes, then enable on-demand populating
tn.PopulateOnDemand = ((int)(dr["childnodecount"]) > 0);
}
}
回答by S.Mohamed
This code runs perfectly for me. Thought it might be useful for somebody looking to display hierarchial data in a treeview.By far, i guess this is the simplest. Please check it out and upvote if it helps you.
这段代码对我来说完美运行。认为它可能对希望在树视图中显示层次结构数据的人有用。到目前为止，我想这是最简单的。如果对您有帮助，请检查并点赞。
Reference : https://techbrij.com/display-hierarchical-data-with-treeview-in-asp-net
参考：https: //techbrij.com/display-hierarchical-data-with-treeview-in-asp-net
C# code:
C#代码：
//dtTree should be accessible in both page load and AddNodes()
//DocsMenu is the treeview Id
DataTable dtTree = new DataTable();
//declare your connection string
protected void Page_Load(object sender, EventArgs e)
{
//DataTable dtTree = new DataTable();
using (con)
{
con.Open();
string sQuery = "Select topicId,parentid,name from tbl_topicMaster";
SqlCommand cmd = new SqlCommand(sQuery, con);
cmd.CommandType = CommandType.Text;
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dtTree);
da.Dispose();
con.Close();
}
AddNodes(-1, DocsMenu.Nodes);
}
void AddNodes(int id, TreeNodeCollection tn)
{
foreach (DataRow dr in dtTree.Select("parentid= " + id))
{
TreeNode sub = new TreeNode(dr["name"].ToString(), dr["topicId"].ToString());
tn.Add(sub);
AddNodes(Convert.ToInt32(sub.Value), sub.ChildNodes);
}
}
aspx code:
aspx代码：
<asp:TreeView ID="DocsMenu" runat="server" ImageSet="BulletedList"
NodeIndent="15" >
<HoverNodeStyle Font-Underline="True" ForeColor="#6666AA" />
<NodeStyle Font-Names="Tahoma" Font-Size="8pt" ForeColor="Black" HorizontalPadding="2px"
NodeSpacing="0px" VerticalPadding="2px"></NodeStyle>
<ParentNodeStyle Font-Bold="False" />
<SelectedNodeStyle BackColor="#B5B5B5" Font-Underline="False" HorizontalPadding="0px"
VerticalPadding="0px" />
</asp:TreeView>
