asp.net C # generate Drop-down list Tree Implementation Code _ Practical Tips

Effect Chart:

Code:

Copy Code code as follows:

Using System.Data;
Using System.Web.UI.WebControls;
<summary>
Generate a Drop-down list tree from a DataTable
</summary>
public class Dropdownlisthelp
{
private string gridline;
Private DataTable DT;
Public Dropdownlisthelp ()
{
//
TODO: Add constructor logic here
//
}
<summary>
Generate a tree Drop-down menu from a DataTable
</summary>
<param name= "DataTable" ></param>
<param name= "Parentkeyfield" > Parent node key field </param>
<param name= "Parentkey" > Parent node Value </param>
<param name= "Keyfield" > This node key field </param>
<param name= "sortstring" > Sort string </param>
<param name= "DDL" >DownList</param>
public void Createdropdowntree (DataTable DataTable, String Parentkeyfield, String Parentkey, String Keyfield, String text Field, String sortstring, DropDownList DDL)
{
DT = DataTable;
Ddl. Items.Add (New ListItem ("", ""));
Addchilditems (Parentkeyfield, Parentkey, Keyfield, TextField, sortstring, DDL);
}
<summary>
Recursive spanning tree node
</summary>
<param name= "Parentkeyfield" > Parent node key field </param>
<param name= "Parentkey" > Parent node Value </param>
<param name= "Keyfield" > This node key field </param>
<param name= "sortstring" > Sort string </param>
<param name= "DDL" >downlist controls </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?) "┗": "Out") + Dv[i][textfield]. ToString (), Dv[i][keyfield]. ToString ()));
Addchilditems (Parentkeyfield, Dv[i][keyfield). ToString (), Keyfield, TextField, sortstring, DDL);
}
Dv. Dispose ();
}
<summary>
A connection line that backtracking spanning a tree
</summary>
<param name= "Parentkeyfield" > Parent node key field </param>
<param name= "Parentkey" > Parent node Value </param>
<param name= "Keyfield" > This node key field </param>
<param name= "Nodekey" > This node value </param>
<param name= "sortstring" > Sort string </param>
<returns></returns>
private void Gettreeline (String Parentkeyfield, String Parentkey, String Keyfield, String Nodekey, String sortstring)
{
Select Parent Layer Node
DataView dv = new DataView (DT, Keyfield + "= '" + Parentkey + "" ", Sortstring, DataViewRowState.CurrentRows);
if (DV. Count > 0)
{
Select parent node Sibling node
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 ();
}
}

Call:

Copy Code code as follows:

Dropdownlisthelp ddlhelper = new Dropdownlisthelp ();
Ddlhelper.createdropdowntree (DT, "ParentID", "1", "ID", "text", "text ASC", DROPDOWNLIST1);