Use treeview to bind data

~ Today, the website is finally launched and in a good mood. It has been tested in the community for a long time at night.
Every day, we hope to have time to learn new technologies.
Today is the treeview control. I was confused before learning it. I thought it was so mysterious,
The principle is: assume a two-level treeview, you only need to bind the depth = 0 node for it, and then bind the depth = 1 node according to the id of the depth = 0 node,
The principle is very simple. It is only a level-1 binding.
I feel that I want to learn a good technology and want to know its functions and display first, so I should first give the code displayed on the page,

<Asp: TreeView ID = "TreeView1" EnableClientScript = "false" runat = "server">
<Nodes>
<Asp: TreeNode SelectAction = "Expand" Expanded = "false" PopulateOnDemand = "true" Text = "website development"> </asp: TreeNode>
</Nodes>
</Asp: TreeView>

The SelectAction attribute is Expand, indicating that the node selection event is expanded, and PopulateOnDemand = true indicates dynamic data binding.
The database is

First, write a database binding method. Private DataSet RunQuery (string command)
{
String strconn = ConfigurationManager. ConnectionStrings ["test"]. ConnectionString;
Using (SqlConnection conn = new SqlConnection (strconn ))
{
Using (SqlCommand cmd = new SqlCommand (command, conn ))
{
SqlDataAdapter da = new SqlDataAdapter (cmd );
DataSet ds = new DataSet ();
Da. Fill (ds );
Return ds;
}
}
}

Set it in webconfig and add using system. data. sqlclient.
Then bind the most advanced node in the legend Private void BindParent (TreeNode node)
{
DataSet ds = RunQuery ("select f_id, f_content from dbo. father ");
If (ds. Tables. Count> 0)
{
Foreach (DataRow row in ds. Tables [0]. Rows)
{
TreeNode newnode = new TreeNode (row ["f_content"]. ToString (), row ["f_id"]. ToString ());
Newnode. SelectAction = TreeNodeSelectAction. Expand;
Newnode. PopulateOnDemand = true;
Node. ChildNodes. Add (newnode );
}
}
}

Second, bind the next level Private void BindChild (TreeNode node)
{
DataSet ds = RunQuery ("select c_content, c_id from dbo. child where c_fid =" + node. Value );
If (ds. Tables. Count> 0)
{
Foreach (DataRow row in ds. Tables [0]. Rows)
{
TreeNode newnode = new TreeNode (row ["c_content"]. ToString (), row ["c_id"]. ToString ());
Newnode. SelectAction = TreeNodeSelectAction. Expand;
Newnode. PopulateOnDemand = true;
Node. ChildNodes. Add (newnode );
}
}
}

Bind the next-level data according to the ID of the previous-level node. This is also true for multiple layers.
Of course, another step is to bind data, that is TreeView1.TreeNodePopulate + = new TreeNodeEventHandler (treeviewappstreenodepopulate );

Protected void treeviewinclutreenodepopulate (object sender, TreeNodeEventArgs e)
{
Switch (e. Node. Depth)
{
Case 0:
BindParent (e. Node );
Break;
Case 1:
BindChild (e. Node );
Break;
}
}

It is actually quite simple to run and generate, right? The running result is as follows (I wrote three layers ),

OK, everything is done. A widget learns the basics and can be expanded slowly. If it is not successful, you can ask for the source code.

Please kindly advise !!!