We can see that Discuz is merged by two drop-down lists. I found some information on the Internet and wrote this small source code. I will share it with you here!
Run the command, as shown in the following figure (the deep black area is not selected, because it is a classification of the upper level ):
The project structure is as follows:
The code of the Controls class library SmartDropDownList. cs is as follows:
SmartDropDownList. cs
Copy codeThe Code is as follows:
Using System;
2 using System. Collections. Generic;
3 using System. Linq;
4 using System. Text;
5 using System. Web. UI. WebControls;
6 using System. Web. UI;
7 using System. ComponentModel;
8 using System. Web;
9
Namespace mydream. Controls
{
[ToolboxData ("<{0}: SmartDropDownList runat = server ></ {0}: SmartDropDownList>")]
Public class SmartDropDownList: DropDownList
{
/// <Summary>
/// Constructor
/// </Summary>
Public SmartDropDownList (){}
/// <Summary>
/// Present the control content to the specified writer
/// </Summary>
/// <Param name = "writer"> </param>
Protected override void RenderContents (HtmlTextWriter writer)
{
OptionGroupRenderContents (writer );
}
/// <Summary>
/// Present Option or OptionGroup
/// </Summary>
/// <Param name = "writer"> writer </param>
Private void OptionGroupRenderContents (HtmlTextWriter writer)
{
// Whether to display the EndTag of OptionGroup
Bool writerEndTag = false;
Foreach (ListItem li in this. Items)
{
// If the optgroup attribute is not present, the Option is displayed.
If (li. Value! = This. OptionGroupValue)
{
// Rendering Option
RenderListItem (li, writer );
}
// If the optgroup attribute exists, OptionGroup is displayed.
Else
{
If (writerEndTag)
// Present the EndTag of OptionGroup
OptionGroupEndTag (writer );
Else
WriterEndTag = true;
// Present the optiintag of OptionGroup
OptionGroupBeginTag (li, writer );
}
}
If (writerEndTag)
// Present the EndTag of OptionGroup
OptionGroupEndTag (writer );
}
/// <Summary>
/// Present the optiintag of OptionGroup
/// </Summary>
/// <Param name = "li"> OptionGroup data item </param>
/// <Param name = "writer"> writer </param>
Private void OptionGroupBeginTag (ListItem li, HtmlTextWriter writer)
{
Writer. WriteBeginTag ("optgroup ");
// Write the OptionGroup label
Writer. WriteAttribute ("label", li. Text );
Foreach (string key in li. Attributes. Keys)
{
// Write other OptionGroup attributes
Writer. WriteAttribute (key, li. Attributes [key]);
}
Writer. Write (HtmlTextWriter. TagRightChar );
Writer. WriteLine ();
}
/// <Summary>
/// Present the EndTag of OptionGroup
/// </Summary>
/// <Param name = "writer"> writer </param>
Private void OptionGroupEndTag (HtmlTextWriter writer)
{
Writer. WriteEndTag ("optgroup ");
Writer. WriteLine ();
}
/// <Summary>
/// Rendering Option
/// </Summary>
/// <Param name = "li"> Option data item </param>
/// <Param name = "writer"> writer </param>
Private void RenderListItem (ListItem li, HtmlTextWriter writer)
{
Writer. WriteBeginTag ("option ");
// Write the Option Value
Writer. WriteAttribute ("value", li. Value, true );
If (li. Selected)
{
// If this Option is selected, it is written to selected.
Writer. WriteAttribute ("selected", "selected", false );
}
Foreach (string key in li. Attributes. Keys)
{
// Write other attributes of Option
Writer. WriteAttribute (key, li. Attributes [key]);
}
Writer. Write (HtmlTextWriter. TagRightChar );
// Write the Text of Option
HttpUtility. HtmlEncode (li. Text, writer );
Writer. WriteEndTag ("option ");
Writer. WriteLine ();
}
/// <Summary>
/// Value of the ListItem used to add the group item of SmartDropDownList
/// </Summary>
[
Browsable (true ),
Description ("Value of ListItem used to add the group items of DropDownList "),
Category ("extension ")
]
Public virtual string OptionGroupValue
{
Get
{
String s = (string) ViewState ["OptionGroupValue"];
Return (s = null )? "Optgroup": s;
}
Set
{
ViewState ["OptionGroupValue"] = value;
}
}
}
}
The code of the smartDropDownList. aspx page is as follows:
SmartDropDownList. aspx
Copy codeThe Code is as follows:
<% @ Page Language = "C #" AutoEventWireup = "true" CodeFile = "smartDropDownList. aspx. cs" Inherits = "smartDropDownList" %>
<% @ Register Assembly = "Controls" Namespace = "mydream. Controls" TagPrefix = "PC3" %>
<! DOCTYPE html PUBLIC "-// W3C // dtd xhtml 1.0 Transitional // EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<Html xmlns = "http://www.w3.org/1999/xhtml">
<Head runat = "server">
<Title> </title>
</Head>
<Body>
<Form id = "form1" runat = "server">
<Div>
<PC3: SmartDropDownList ID = "SmartDropDownList1" runat = "server">
</PC3: SmartDropDownList>
</Div>
</Form>
</Body>
</Html>
SmartDropDownList. aspx page smartDropDownList. cs is as follows:
SmartDropDownList. cs
Copy codeThe Code is as follows:
Using System;
Using System. Collections. Generic;
Using System. Linq;
Using System. Web;
Using System. Web. UI;
Using System. Web. UI. WebControls;
Using System. Data;
Public partial class smartDropDownList: System. Web. UI. Page
{
Protected void Page_Load (object sender, EventArgs e)
{
If (! IsPostBack)
{
This. Bindddlist (this. SmartDropDownList1 );
}
}
/// <Summary>
/// Plate ListItem
/// </Summary>
/// <Returns> </returns>
Private List <ListItem> GetBoardList ()
{
List <ListItem> list = new List <ListItem> ();
For (int I = 1; I <6; I ++)
{
ListItem li = new ListItem ("here is the section" + I, I. ToString ());
List. Add (li );
}
Return list;
}
/// <Summary>
/// Submodule ListItem
/// </Summary>
/// <Returns> </returns>
Private List <ListItem> GetSubBoardList ()
{
List <ListItem> list = this. GetBoardList ();
List <ListItem> list_sub = new List <ListItem> ();
Foreach (ListItem li in list)
{
ListItem li_sub = new ListItem ("This item is a subsection of the upper level", "Here is the value of the parameter you want to pass ");
List_sub.Add (li_sub );
}
Return list_sub;
}
/// <Summary>
/// Bind the drop-down control data
/// </Summary>
Private void Bindddlist (mydream. Controls. SmartDropDownList smartddlist)
{
Smartddlist. Items. Clear ();
List <ListItem> list = this. GetBoardList ();
Foreach (ListItem li in list)
{
ListItem item = new ListItem ("--" + li. Text, "optgroup ");
Smartddlist. Items. Add (item );
List <ListItem> list_sub = this. GetSubBoardList ();
Foreach (ListItem li_sub in list_sub)
{
Smartddlist. Items. Add (li_sub );
}
}
Smartddlist. DataBind ();
}
}
You can bind a value based on your database design. There is no database here, just to illustrate the concept!
Download the source code. Click here!
Copyright. For more information, see the source!
