There are two tables with the following structure:
Table province structure: province_id province_name (primary key: province_id)
Table city structure: city_id, city_name, province_id (primary key: city_id, province_id) SqlConnection conn = new SqlConnection ("server = Beijing; integrated security = sspi; database = test ");
SqlDataAdapter da;
DataSet ds = new DataSet ();
Private void Form1_Load (object sender, EventArgs e)
{
ReadNodes ();
This. treeView1.ExpandAll ();
}
Private void readNodes ()
{
String _ SQL = "select * from province ";
Da = new SqlDataAdapter (_ SQL, conn );
Da. Fill (ds, "province ");
DataView dvw1 = new DataView (ds. Tables ["province"]);
Int I = 0;
Foreach (DataRowView myRow1 in dvw1)
{
String strProvinceName = myRow1 ["province_name"]. ToString (). Trim ();
This. treeView1.Nodes. Add (new TreeNode (strProvinceName); // read ParentNode
// Certificate //---------------------------------------------------------------------------------------------------------------------------------------//
Da = new SqlDataAdapter ("select * from city where province_id = '" + myRow1 ["province_id"]. ToString (). Trim () + "'", conn );
Da. Fill (ds, "city ");
DataView dvw2 = new DataView (ds. Tables ["city"]);
Foreach (DataRowView myRow2 in dvw2)
{
String strCityName = myRow2 ["city_name"]. ToString (). Trim ();
This. treeView1.Nodes [I]. Nodes. Add (new TreeNode (strCityName); // read ChildNode
}
I ++;
Ds. Tables ["city"]. Clear ();
This. treeView1.SelectedNode = treeView1.Nodes [0];
}
}
The result is as follows:
Note: The TreeView shown in the code above only supports a 2-layer tree structure (related to the Table structure I tested). The method is relatively primitive, if you want to expand, you can use recursive calls to achieve node reading of the tree structure!
