Can anyone recommend a dropdownlist control for asp.net (3.5) that can render option groups? Thanks
I've used the standard control in the past, and just added a simple ControlAdapter for it that would override the default behavior so it could render <optgroup>s in certain places. Here is the class I used (VB.Net). Note that this was for a specific purpose and written in .Net 2.0, so it may not suit you as well. But it should give you a starting point at least. Also, you have to hook it up using a .browserfile in your project.
''#This codes makes the dropdownlist control recognize items with "--"'
''#for the label or items with an OptionGroup attribute and render them'
''#as <optgroup> instead of <option>.'
Public Class DropDownListAdapter
Inherits System.Web.UI.WebControls.Adapters.WebControlAdapter
Protected Overrides Sub RenderContents(ByVal writer As HtmlTextWriter)
Dim list As DropDownList = Me.Control
Dim currentOptionGroup As String
Dim renderedOptionGroups As New Generic.List(Of String)
For Each item As ListItem In list.Items
If item.Attributes("OptionGroup") IsNot Nothing Then
''#The item is part of an option group
currentOptionGroup = item.Attributes("OptionGroup")
If (renderedOptionGroups.Contains(currentOptionGroup)) Then
''#the option header was already written, just render the list item
RenderListItem(item, writer)
Else
''#the header was not written- do that first
If (renderedOptionGroups.Count > 0) Then
RenderOptionGroupEndTag(writer) ''#need to close previous group
End If
RenderOptionGroupBeginTag(currentOptionGroup, writer)
renderedOptionGroups.Add(currentOptionGroup)
RenderListItem(item, writer)
End If
ElseIf item.Text = "--" Then ''#simple separator
RenderOptionGroupBeginTag("--", writer)
RenderOptionGroupEndTag(writer)
Else
''#default behavior: render the list item as normal
RenderListItem(item, writer)
End If
Next item
If renderedOptionGroups.Count > 0 Then
RenderOptionGroupEndTag(writer)
End If
End Sub
Private Sub RenderOptionGroupBeginTag(ByVal name As String, ByVal writer As HtmlTextWriter)
writer.WriteBeginTag("optgroup")
writer.WriteAttribute("label", name)
writer.Write(HtmlTextWriter.TagRightChar)
writer.WriteLine()
End Sub
Private Sub RenderOptionGroupEndTag(ByVal writer As HtmlTextWriter)
writer.WriteEndTag("optgroup")
writer.WriteLine()
End Sub
Private Sub RenderListItem(ByVal item As ListItem, ByVal writer As HtmlTextWriter)
writer.WriteBeginTag("option")
writer.WriteAttribute("value", item.Value, True)
If item.Selected Then
writer.WriteAttribute("selected", "selected", False)
End If
For Each key As String In item.Attributes.Keys
writer.WriteAttribute(key, item.Attributes(key))
Next key
writer.Write(HtmlTextWriter.TagRightChar)
HttpUtility.HtmlEncode(item.Text, writer)
writer.WriteEndTag("option")
writer.WriteLine()
End Sub
End Class
My browser file was named "App_Browsers\BrowserFile.browser" and looked like this:
<!--
You can find existing browser definitions at
<windir>\Microsoft.NET\Framework\<ver>\CONFIG\Browsers
-->
<browsers>
<browser refID="Default">
<controlAdapters>
<adapter controlType="System.Web.UI.WebControls.DropDownList"
adapterType="DropDownListAdapter" />
</controlAdapters>
</browser>
</browsers>
The Sharp Pieces project on CodePlex solves this (and several other) control limitations.
Thanks Joel! everyone... here's C# version if you want it:
using System;
using System.Web.UI.WebControls.Adapters;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections.Generic;
using System.Web;
//This codes makes the dropdownlist control recognize items with "--"'
//for the label or items with an OptionGroup attribute and render them'
//as instead of .'
public class DropDownListAdapter : WebControlAdapter
{
protected override void RenderContents(HtmlTextWriter writer)
{
DropDownList list = Control as DropDownList;
string currentOptionGroup;
List renderedOptionGroups = new List();
foreach(ListItem item in list.Items)
{
if (item.Attributes["OptionGroup"] != null)
{
//'The item is part of an option group'
currentOptionGroup = item.Attributes["OptionGroup"];
//'the option header was already written, just render the list item'
if(renderedOptionGroups.Contains(currentOptionGroup))
RenderListItem(item, writer);
else
{
//the header was not written- do that first'
if (renderedOptionGroups.Count > 0)
RenderOptionGroupEndTag(writer); //'need to close previous group'
RenderOptionGroupBeginTag(currentOptionGroup, writer);
renderedOptionGroups.Add(currentOptionGroup);
RenderListItem(item, writer);
}
}
else if (item.Text == "--") //simple separator
{
RenderOptionGroupBeginTag("--", writer);
RenderOptionGroupEndTag(writer);
}
else
{
//default behavior: render the list item as normal'
RenderListItem(item, writer);
}
}
if(renderedOptionGroups.Count > 0)
RenderOptionGroupEndTag(writer);
}
private void RenderOptionGroupBeginTag(string name, HtmlTextWriter writer)
{
writer.WriteBeginTag("optgroup");
writer.WriteAttribute("label", name);
writer.Write(HtmlTextWriter.TagRightChar);
writer.WriteLine();
}
private void RenderOptionGroupEndTag(HtmlTextWriter writer)
{
writer.WriteEndTag("optgroup");
writer.WriteLine();
}
private void RenderListItem(ListItem item, HtmlTextWriter writer)
{
writer.WriteBeginTag("option");
writer.WriteAttribute("value", item.Value, true);
if (item.Selected)
writer.WriteAttribute("selected", "selected", false);
foreach (string key in item.Attributes.Keys)
writer.WriteAttribute(key, item.Attributes[key]);
writer.Write(HtmlTextWriter.TagRightChar);
HttpUtility.HtmlEncode(item.Text, writer);
writer.WriteEndTag("option");
writer.WriteLine();
}
}
Hello guys,
I use the reflector to see why is not supported. There is why. In the render method of the ListControl no condition is there to create the optgroup.
protected internal override void RenderContents(HtmlTextWriter writer)
{
ListItemCollection items = this.Items;
int count = items.Count;
if (count > 0)
{
bool flag = false;
for (int i = 0; i < count; i++)
{
ListItem item = items[i];
if (item.Enabled)
{
writer.WriteBeginTag("option");
if (item.Selected)
{
if (flag)
{
this.VerifyMultiSelect();
}
flag = true;
writer.WriteAttribute("selected", "selected");
}
writer.WriteAttribute("value", item.Value, true);
if (item.HasAttributes)
{
item.Attributes.Render(writer);
}
if (this.Page != null)
{
this.Page.ClientScript.RegisterForEventValidation(this.UniqueID, item.Value);
}
writer.Write('>');
HttpUtility.HtmlEncode(item.Text, writer);
writer.WriteEndTag("option");
writer.WriteLine();
}
}
}
}
So i create my own dropdown Control with an override of the method RenderContents. There is my control. Is working fine. I use exactly the same code of Microsoft, just add a little condition to support listItem having attribute optgroup to create an optgroup and not a option.
Give me some feed back
public class DropDownListWithOptionGroup : DropDownList
{
public const string OptionGroupTag = "optgroup";
private const string OptionTag = "option";
protected override void RenderContents(System.Web.UI.HtmlTextWriter writer)
{
ListItemCollection items = this.Items;
int count = items.Count;
string tag;
string optgroupLabel;
if (count > 0)
{
bool flag = false;
for (int i = 0; i < count; i++)
{
tag = OptionTag;
optgroupLabel = null;
ListItem item = items[i];
if (item.Enabled)
{
if (item.Attributes != null && item.Attributes.Count > 0 && item.Attributes[OptionGroupTag] != null)
{
tag = OptionGroupTag;
optgroupLabel = item.Attributes[OptionGroupTag];
}
writer.WriteBeginTag(tag);
// NOTE(cboivin): Is optionGroup
if (!string.IsNullOrEmpty(optgroupLabel))
{
writer.WriteAttribute("label", optgroupLabel);
}
else
{
if (item.Selected)
{
if (flag)
{
this.VerifyMultiSelect();
}
flag = true;
writer.WriteAttribute("selected", "selected");
}
writer.WriteAttribute("value", item.Value, true);
if (item.Attributes != null && item.Attributes.Count > 0)
{
item.Attributes.Render(writer);
}
if (this.Page != null)
{
this.Page.ClientScript.RegisterForEventValidation(this.UniqueID, item.Value);
}
}
writer.Write('>');
HttpUtility.HtmlEncode(item.Text, writer);
writer.WriteEndTag(tag);
writer.WriteLine();
}
}
}
}
}
As the answers above that overload the RenderContents method do work. You also have to remember to alter the viewstate. I have come into an issue when using the non-altered viewstate in UpdatePanels. This has parts taken from the Sharp Pieces Project.
Protected Overloads Overrides Sub RenderContents(ByVal writer As HtmlTextWriter)
Dim list As DropDownList = Me
Dim currentOptionGroup As String
Dim renderedOptionGroups As New List(Of String)()
For Each item As ListItem In list.Items
If item.Attributes("OptionGroup") Is Nothing Then
RenderListItem(item, writer)
Else
currentOptionGroup = item.Attributes("OptionGroup")
If renderedOptionGroups.Contains(currentOptionGroup) Then
RenderListItem(item, writer)
Else
If renderedOptionGroups.Count > 0 Then
RenderOptionGroupEndTag(writer)
End If
RenderOptionGroupBeginTag(currentOptionGroup, writer)
renderedOptionGroups.Add(currentOptionGroup)
RenderListItem(item, writer)
End If
End If
Next
If renderedOptionGroups.Count > 0 Then
RenderOptionGroupEndTag(writer)
End If
End Sub
Private Sub RenderOptionGroupBeginTag(ByVal name As String, ByVal writer As HtmlTextWriter)
writer.WriteBeginTag("optgroup")
writer.WriteAttribute("label", name)
writer.Write(HtmlTextWriter.TagRightChar)
writer.WriteLine()
End Sub
Private Sub RenderOptionGroupEndTag(ByVal writer As HtmlTextWriter)
writer.WriteEndTag("optgroup")
writer.WriteLine()
End Sub
Private Sub RenderListItem(ByVal item As ListItem, ByVal writer As HtmlTextWriter)
writer.WriteBeginTag("option")
writer.WriteAttribute("value", item.Value, True)
If item.Selected Then
writer.WriteAttribute("selected", "selected", False)
End If
For Each key As String In item.Attributes.Keys
writer.WriteAttribute(key, item.Attributes(key))
Next
writer.Write(HtmlTextWriter.TagRightChar)
HttpUtility.HtmlEncode(item.Text, writer)
writer.WriteEndTag("option")
writer.WriteLine()
End Sub
Protected Overrides Function SaveViewState() As Object
' Create an object array with one element for the CheckBoxList's
' ViewState contents, and one element for each ListItem in skmCheckBoxList
Dim state(Me.Items.Count + 1 - 1) As Object 'stupid vb array
Dim baseState As Object = MyBase.SaveViewState()
state(0) = baseState
' Now, see if we even need to save the view state
Dim itemHasAttributes As Boolean = False
For i As Integer = 0 To Me.Items.Count - 1
If Me.Items(i).Attributes.Count > 0 Then
itemHasAttributes = True
' Create an array of the item's Attribute's keys and values
Dim attribKV(Me.Items(i).Attributes.Count * 2 - 1) As Object 'stupid vb array
Dim k As Integer = 0
For Each key As String In Me.Items(i).Attributes.Keys
attribKV(k) = key
k += 1
attribKV(k) = Me.Items(i).Attributes(key)
k += 1
Next
state(i + 1) = attribKV
End If
Next
' return either baseState or state, depending on whether or not
' any ListItems had attributes
If (itemHasAttributes) Then
Return state
Else
Return baseState
End If
End Function
Protected Overrides Sub LoadViewState(ByVal savedState As Object)
If savedState Is Nothing Then Return
' see if savedState is an object or object array
If Not savedState.GetType.GetElementType() Is Nothing AndAlso savedState.GetType.GetElementType().Equals(GetType(Object)) Then
' we have just the base state
MyBase.LoadViewState(savedState(0))
'we have an array of items with attributes
Dim state() As Object = savedState
MyBase.LoadViewState(state(0)) '/ load the base state
For i As Integer = 1 To state.Length - 1
If Not state(i) Is Nothing Then
' Load back in the attributes
Dim attribKV() As Object = state(i)
For k As Integer = 0 To attribKV.Length - 1 Step +2
Me.Items(i - 1).Attributes.Add(attribKV(k).ToString(), attribKV(k + 1).ToString())
Next
End If
Next
Else
'load it normal
MyBase.LoadViewState(savedState)
End If
End Sub
Hi,
I have used JQuery to achieve this task. I first added an new attribute for every ListItem from the backend and then used that attribute in JQuery wrapAll() method to create groups
Backend Code
foreach (ListItem item in ((DropDownList)sender).Items)
{
if (System.Int32.Parse(item.Value) < 5)
item.Attributes.Add("classification", "LessThanFive");
else
item.Attributes.Add("classification", "GreaterThanFive");
}
JQuery Part:
<script>
$(document).ready(function() {
//Create groups for dropdown list
$("select.listsmall option[@classification='LessThanFive']").wrapAll("<optgroup label='Less than five'>");
$("select.listsmall option[@classification='GreaterThanFive']").wrapAll("<optgroup label='Greater than five'>");
});
</script>
You can see the output here...
Dropdownlist control with grouping ()
Based on the posts above I've created a c# version of this control with working view state.
public const string OptionGroupTag = "optgroup";
private const string OptionTag = "option";
protected override void RenderContents(System.Web.UI.HtmlTextWriter writer)
{
ListItemCollection items = this.Items;
int count = items.Count;
string tag;
string optgroupLabel;
if (count > 0)
{
bool flag = false;
for (int i = 0; i < count; i++)
{
tag = OptionTag;
optgroupLabel = null;
ListItem item = items[i];
if (item.Enabled)
{
if (item.Attributes != null && item.Attributes.Count > 0 && item.Attributes[OptionGroupTag] != null)
{
tag = OptionGroupTag;
optgroupLabel = item.Attributes[OptionGroupTag];
}
writer.WriteBeginTag(tag);
// NOTE(cboivin): Is optionGroup
if (!string.IsNullOrEmpty(optgroupLabel))
{
writer.WriteAttribute("label", optgroupLabel);
}
else
{
if (item.Selected)
{
if (flag)
{
this.VerifyMultiSelect();
}
flag = true;
writer.WriteAttribute("selected", "selected");
}
writer.WriteAttribute("value", item.Value, true);
if (item.Attributes != null && item.Attributes.Count > 0)
{
item.Attributes.Render(writer);
}
if (this.Page != null)
{
this.Page.ClientScript.RegisterForEventValidation(this.UniqueID, item.Value);
}
}
writer.Write('>');
HttpUtility.HtmlEncode(item.Text, writer);
writer.WriteEndTag(tag);
writer.WriteLine();
}
}
}
}
protected override object SaveViewState()
{
object[] state = new object[this.Items.Count + 1];
object baseState = base.SaveViewState();
state[0] = baseState;
bool itemHasAttributes = false;
for (int i = 0; i < this.Items.Count; i++)
{
if (this.Items[i].Attributes.Count > 0)
{
itemHasAttributes = true;
object[] attributes = new object[this.Items[i].Attributes.Count * 2];
int k = 0;
foreach (string key in this.Items[i].Attributes.Keys)
{
attributes[k] = key;
k++;
attributes[k] = this.Items[i].Attributes[key];
k++;
}
state[i + 1] = attributes;
}
}
if (itemHasAttributes)
return state;
return baseState;
}
protected override void LoadViewState(object savedState)
{
if (savedState == null)
return;
if (!(savedState.GetType().GetElementType() == null) &&
(savedState.GetType().GetElementType().Equals(typeof(object))))
{
object[] state = (object[])savedState;
base.LoadViewState(state[0]);
for (int i = 1; i < state.Length; i++)
{
if (state[i] != null)
{
object[] attributes = (object[])state[i];
for (int k = 0; k < attributes.Length; k += 2)
{
this.Items[i - 1].Attributes.Add
(attributes[k].ToString(), attributes[k + 1].ToString());
}
}
}
}
else
{
base.LoadViewState(savedState);
}
}
I hope this helps some people :-)
The above code renders the end tag for the optgroup before any of the options, so the options don't get indented like they should in addition to the markup not properly representing the grouping. Here's my slightly modified version of Tom's code:
public class ExtendedDropDownList : System.Web.UI.WebControls.DropDownList
{
public const string OptionGroupTag = "optgroup";
private const string OptionTag = "option";
protected override void RenderContents(System.Web.UI.HtmlTextWriter writer)
{
ListItemCollection items = this.Items;
int count = items.Count;
string tag;
string optgroupLabel;
if (count > 0)
{
bool flag = false;
string prevOptGroup = null;
for (int i = 0; i < count; i++)
{
tag = OptionTag;
optgroupLabel = null;
ListItem item = items[i];
if (item.Enabled)
{
if (item.Attributes != null && item.Attributes.Count > 0 && item.Attributes[OptionGroupTag] != null)
{
optgroupLabel = item.Attributes[OptionGroupTag];
if (prevOptGroup != optgroupLabel)
{
if (prevOptGroup != null)
{
writer.WriteEndTag(OptionGroupTag);
}
writer.WriteBeginTag(OptionGroupTag);
if (!string.IsNullOrEmpty(optgroupLabel))
{
writer.WriteAttribute("label", optgroupLabel);
}
writer.Write('>');
}
item.Attributes.Remove(OptionGroupTag);
prevOptGroup = optgroupLabel;
}
else
{
if (prevOptGroup != null)
{
writer.WriteEndTag(OptionGroupTag);
}
prevOptGroup = null;
}
writer.WriteBeginTag(tag);
if (item.Selected)
{
if (flag)
{
this.VerifyMultiSelect();
}
flag = true;
writer.WriteAttribute("selected", "selected");
}
writer.WriteAttribute("value", item.Value, true);
if (item.Attributes != null && item.Attributes.Count > 0)
{
item.Attributes.Render(writer);
}
if (optgroupLabel != null)
{
item.Attributes.Add(OptionGroupTag, optgroupLabel);
}
if (this.Page != null)
{
this.Page.ClientScript.RegisterForEventValidation(this.UniqueID, item.Value);
}
writer.Write('>');
HttpUtility.HtmlEncode(item.Text, writer);
writer.WriteEndTag(tag);
writer.WriteLine();
if (i == count - 1)
{
if (prevOptGroup != null)
{
writer.WriteEndTag(OptionGroupTag);
}
}
}
}
}
}
protected override object SaveViewState()
{
object[] state = new object[this.Items.Count + 1];
object baseState = base.SaveViewState();
state[0] = baseState;
bool itemHasAttributes = false;
for (int i = 0; i < this.Items.Count; i++)
{
if (this.Items[i].Attributes.Count > 0)
{
itemHasAttributes = true;
object[] attributes = new object[this.Items[i].Attributes.Count * 2];
int k = 0;
foreach (string key in this.Items[i].Attributes.Keys)
{
attributes[k] = key;
k++;
attributes[k] = this.Items[i].Attributes[key];
k++;
}
state[i + 1] = attributes;
}
}
if (itemHasAttributes)
return state;
return baseState;
}
protected override void LoadViewState(object savedState)
{
if (savedState == null)
return;
if (!(savedState.GetType().GetElementType() == null) &&
(savedState.GetType().GetElementType().Equals(typeof(object))))
{
object[] state = (object[])savedState;
base.LoadViewState(state[0]);
for (int i = 1; i < state.Length; i++)
{
if (state[i] != null)
{
object[] attributes = (object[])state[i];
for (int k = 0; k < attributes.Length; k += 2)
{
this.Items[i - 1].Attributes.Add
(attributes[k].ToString(), attributes[k + 1].ToString());
}
}
}
}
else
{
base.LoadViewState(savedState);
}
}
}
Use it like this:
ListItem item1 = new ListItem("option1");
item1.Attributes.Add("optgroup", "CatA");
ListItem item2 = new ListItem("option2");
item2.Attributes.Add("optgroup", "CatA");
ListItem item3 = new ListItem("option3");
item3.Attributes.Add("optgroup", "CatB");
ListItem item4 = new ListItem("option4");
item4.Attributes.Add("optgroup", "CatB");
ListItem item5 = new ListItem("NoOptGroup");
ddlTest.Items.Add(item1);
ddlTest.Items.Add(item2);
ddlTest.Items.Add(item3);
ddlTest.Items.Add(item4);
ddlTest.Items.Add(item5);
and here's the generated markup (indented for ease of viewing):
<select name="ddlTest" id="Select1">
<optgroup label="CatA">
<option selected="selected" value="option1">option1</option>
<option value="option2">option2</option>
</optgroup>
<optgroup label="CatB">
<option value="option3">option3</option>
<option value="option4">option4</option>
</optgroup>
<option value="NoOptGroup">NoOptGroup</option>
</select>