Creating Multiselect DropDownList Control In ASP.NET 4.0 Using Bootstrap: Part 2

This article is in continuation of my previous article on creating a multiselect dropdownlist using bootstrap in ASP.NET. If you haven’t had a look at it please go through the following link.

•  Creating Multiselect DropDownList Control in ASP.NET 4.0 Using Bootstrap

In the above article we simply developed a bootstrap Multiselect DropDownList user control with less features. The following are the merits and demerits of the built control:

Merits

• It allows the user to select multiple items from a dropdownlist at a single point of time.
• By setting a single property we can make the control as “Multi Select” or “Single Select”.
• We also saw that the control is capable of maintaining its state during postback / server round trips.

Demerits

• The control is not making full use of JavaScript features such as polymorphism, method overriding, etc.
• Also it lacks server side properties of dropdownlist like AutoPostBack, ValidationGroup, SelectedIndexChanged event, etc.
• Did not impose any validation like requiredField validator on the dropdownlist control.
• UI wise improvement can be done.

In this article we’ll try to enhance our user control so that all the drawbacks can be taken care of. So let’s update our control properties and script files accordingly.

AutoCompleteDdl.aspx code

<%@ControlLanguage="C#"AutoEventWireup="true"CodeFile="AutoCompleteDdl.ascx.cs"Inherits="User_Control_AutoCompleteDdl"%>
<divstyledivstyledivstyledivstyledivstyledivstyledivstyledivstyle="width: 380px;"id="divAutoComplete"runat="server">
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnButtonWidth"runat="server"Value="320px"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnNonSelectedText"runat="server"Value="--Select--"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnIncludeSelectAllOption"runat="server"Value="false"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnSelectAllText"runat="server"Value="All"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnEnableFiltering"runat="server"Value="False"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnEnableFilteringIgnoreCase"runat="server"Value="False"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnDisableIfEmpty"runat="server"Value="False"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnMaxHeight"runat="server"Value="200"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnFilterPlaceholder"runat="server"Value="Search for something..."/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnAllSelectedText"runat="server"Value="No option left..."/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnText"runat="server"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnValue"runat="server"/>
    <asp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldIDasp:HiddenFieldID="hdnSelectionMode"runat="server"Value="checkbox"/>
    <asp:ListBoxIDasp:ListBoxIDasp:ListBoxIDasp:ListBoxIDasp:ListBoxIDasp:ListBoxIDasp:ListBoxIDasp:ListBoxID="ddlAutoCompleteSelect"runat="server"Style="width: 350px;"
SelectionMode="Multiple"OnSelectedIndexChanged="ddlAutoCompleteSelect_SelectedIndexChanged1">
    </asp:ListBox>
    <!--Adding RequiredField Validator-->
    <asp:RequiredFieldValidatorIDasp:RequiredFieldValidatorIDasp:RequiredFieldValidatorIDasp:RequiredFieldValidatorIDasp:RequiredFieldValidatorIDasp:RequiredFieldValidatorIDasp:RequiredFieldValidatorIDasp:RequiredFieldValidatorID="reqddlAutoCompleteSelect"runat="server"ControlToValidate="ddlAutoCompleteSelect"
InitialValue=""Display="Dynamic"Enabled="False"ForeColor="Red">
    </asp:RequiredFieldValidator>
    <p>
        <asp:LabelIDasp:LabelIDasp:LabelIDasp:LabelIDasp:LabelIDasp:LabelIDasp:LabelIDasp:LabelID="lblSelectedItems"runat="server"Style="word-wrap: break-word; height: auto; float: left; overflow-y: auto; display: none;">
        </asp:Label>
    </p>
</div>

AutoCompleteDdl.aspx.cs

using System;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Web;
usingSystem.Web.UI;
usingSystem.Web.UI.WebControls;

publicpartialclassUser_Control_AutoCompleteDdl: System.Web.UI.UserControl {#region Variable Declarations

    privateconststring _dataTextField = "Text";
    privateconststring _dataValueField = "Value";
    publiceventEventHandlerSelectedIndexChanged;

    #endregion

    #region Properties

    #regionBootStrap Properties

    ///<summary>
    ///Set the placeholder for the DropDownlist.
    ///</summary>
    publicstringNonSelectedText
    {
        get
        {
            returnhdnNonSelectedText.Value;
        }
        set
        {
            hdnNonSelectedText.Value = value;
        }
    }

    ///<summary>
    /// Get Or Set the value whether select all option should be included or not.
    ///</summary>
    publicboolIncludeSelectAllOption
    {
        get
        {
            returnConvert.ToBoolean(hdnIncludeSelectAllOption.Value);
        }
        set
        {
            //For radio Button or Single Select there is no need of including the selectAll Option/checkBox button.
            //That's why the default value of "false" is set even if the value is "True".
            if (value == true && SelectionMode == ListSelectionMode.Single) {
                hdnIncludeSelectAllOption.Value = "false";
            }
            else
            {
                hdnIncludeSelectAllOption.Value = Convert.ToString(value);
            }
        }
    }

    ///<summary>
    /// Get Or Set the value wheter filter is enabled or not.
    ///</summary>
    publicboolEnableFiltering
    {
        get
        {
            returnConvert.ToBoolean(hdnEnableFiltering.Value);
        }
        set
        {
            hdnEnableFiltering.Value = Convert.ToString(value);
        }
    }

    ///<summary>
    /// Set the Width of the Combo
    ///</summary>
    publicstringButtonWidth
    {
        get
        {
            returnhdnButtonWidth.Value;
        }
        set
        {
            hdnButtonWidth.Value = value;
            lblSelectedItems.Style.Add("width", hdnButtonWidth.Value);
        }
    }

    ///<summary>
    /// Get Or Set the value to disable dropdownlist when it is empty.
    ///</summary>
    publicboolDisableIfEmpty
    {
        get
        {
            returnConvert.ToBoolean(hdnDisableIfEmpty.Value);
        }
        set
        {
            hdnDisableIfEmpty.Value = Convert.ToString(value);
        }
    }

    ///<summary>
    /// Get Or Set the value the maximum height for the control.
    ///</summary>
    publicintMaxHeight
    {
        get
        {
            returnConvert.ToInt32(hdnMaxHeight.Value);
        }
        set
        {
            hdnMaxHeight.Value = Convert.ToString(value);
        }
    }

    ///<summary>
    /// Get Or Set the value for select all option.
    ///</summary>
    publicstringSelectAllText
    {
        get
        {
            returnhdnSelectAllText.Value;
        }
        set
        {
            hdnSelectAllText.Value = value;
        }
    }

    ///<summary>
    /// Get Or Set the value whether select all option should be there or not.
    ///</summary>
    publicboolEnableFilteringIgnoreCase
    {
        get
        {
            returnConvert.ToBoolean(hdnEnableFilteringIgnoreCase.Value);
        }
        set
        {
            hdnEnableFilteringIgnoreCase.Value = Convert.ToString(value);
        }
    }

    publicstringFilterPlaceholder
    {
        get
        {
            returnhdnFilterPlaceholder.Value;
        }
        set
        {
            hdnFilterPlaceholder.Value = value;
        }
    }


    #endregion

    #regionListView Properties

    publicstringGetID
    {
        get
        {
            returnthis.ID;
        }
    }

    publicstringGetClientID
    {
        get
        {
            returnthis.ClientID + "_ddlAutoCompleteSelect";
        }
    }

    ///<summary>
    ///To set text search enabled
    ///</summary>
    publicbool Enabled
    {
        get
        {
            returnddlAutoCompleteSelect.Enabled;
        }
        set
        {
            ddlAutoCompleteSelect.Enabled = value;
        }
    }

    ///<summary>
    ///Sets the Type of DropDownlist it is. For e.g. whether single select or multi select.
    ///</summary>
    publicListSelectionModeSelectionMode
    {
        get
        {
            returnddlAutoCompleteSelect.SelectionMode;
        }
        set
        {
            if (value == ListSelectionMode.Single)
            {
                ddlAutoCompleteSelect.SelectionMode = ListSelectionMode.Single;
                hdnSelectionMode.Value = "radio";
            }
            else
            {
                ddlAutoCompleteSelect.SelectionMode = ListSelectionMode.Multiple;
                hdnSelectionMode.Value = "checkbox";
            }
        }
    }

    ///<summary>
    ///To set Data Source for Control
    ///</summary>
    publicList < SelectModel > DataSource
    {
        set
        {
            ddlAutoCompleteSelect.DataSource = value;
            ddlAutoCompleteSelect.DataBind();
        }
    }

    ///<summary>
    ///To set Text field
    ///</summary>
    publicstringDataTextField
    {
        get
        {
            returnddlAutoCompleteSelect.DataTextField;
        }
        //If String.IsNullOrEmpty(value) Then
        //    value = _dataTextField
        //End If
        set
        {
            ddlAutoCompleteSelect.DataTextField = _dataTextField;
        }
    }

    ///<summary>
    ///To set Value field
    ///</summary>
    publicstringDataValueField
    {
        get
        {
            returnddlAutoCompleteSelect.DataValueField;
        }
        //If String.IsNullOrEmpty(value) Then
        //    value = _dataValueField
        //End If
        set
        {
            ddlAutoCompleteSelect.DataValueField = _dataValueField;
        }
    }

    ///<summary>
    /// Get the value of the Selected Items from the dropdownlist.
    ///</summary>
    publicstring Value
    {
        get
        {
            returnhdnValue.Value;
        }
    }

    ///<summary>
    /// Get the text of the Selected Items from the dropdownlist.
    ///</summary>
    publicstring Text
    {
        get
        {
            returnhdnText.Value;
        }
    }

    ///<summary>
    ///This property is used for setting the auto postback property of the control.
    ///</summary>
    publicboolAutoPostBack
    {
        get
        {
            returnddlAutoCompleteSelect.AutoPostBack;
        }
        set
        {
            ddlAutoCompleteSelect.AutoPostBack = value;
        }
    }

    ///<summary>
    /// Returns the list of dropdownlist items.
    ///</summary>
    publicListItemCollection Items
    {
        get
        {
            returnddlAutoCompleteSelect.Items;
        }
    }

    ///<summary>
    ///Gets Or Sets the selected Index of the dropdownlist.
    ///</summary>
    publicintSelectedIndex
    {
        get
        {
            returnddlAutoCompleteSelect.SelectedIndex;
        }
        set
        {
            ddlAutoCompleteSelect.SelectedIndex = value;
        }
    }

    publicListItemSelectedItem
    {
        get
        {
            returnddlAutoCompleteSelect.SelectedItem;
        }
    }
    ///<summary>
    /// Get Or Sets the selected value of the dropdownlist.
    ///</summary>
    publicstringSelectedValue
    {
        get
        {
            returnddlAutoCompleteSelect.SelectedValue;
        }
        set
        {
            if ((ddlAutoCompleteSelect.Items.Count > 0 && !value.Equals("0") && !value.Equals("")))
            {
                ddlAutoCompleteSelect.SelectedValue = value;
            }
        }
    }

    ///<summary>
    /// Get Or Sets the error Message to the requiredFieldValidator.
    ///</summary>
    publicstringErrorMessage
    {
        get
        {
            returnreqddlAutoCompleteSelect.ErrorMessage;
        }
        set
        {
            reqddlAutoCompleteSelect.ErrorMessage = value;
        }
    }

    publicboolEnableValidation
    {
        get
        {
            returnddlAutoCompleteSelect.CausesValidation;
        }
        set
        {
            reqddlAutoCompleteSelect.Enabled = value;
            ddlAutoCompleteSelect.CausesValidation = value;
        }
    }

    publicstringRequiredFieldValidationGroup
    {
        get
        {
            returnreqddlAutoCompleteSelect.ValidationGroup;
        }

        set
        {
            reqddlAutoCompleteSelect.ValidationGroup = value;
        }
    }

    publicstringDropDownValidationGroup
    {
        get
        {
            returnddlAutoCompleteSelect.ValidationGroup;
        }
        set
        {
            ddlAutoCompleteSelect.ValidationGroup = value;
        }
    }

    #endregion

    #endregion

    #region Page Events

    protectedvoidPage_Load(object sender, System.EventArgs e)
    {
        try
        {
            if (!(string.IsNullOrEmpty(hdnText.Value) && string.IsNullOrEmpty(hdnValue.Value)))
            {
                string[] selectedItemsText = hdnText.Value.Split(newchar[]
                {
                    ','
                }, StringSplitOptions.RemoveEmptyEntries);
                string[] selectedItemsValue = hdnValue.Value.Split(newchar[]
                {
                    ','
                }, StringSplitOptions.RemoveEmptyEntries);

                IEnumerable < ListItem > listItems = ddlAutoCompleteSelect.Items.Cast < ListItem > ().Where(x => selectedItemsText.Contains(x.Text) && selectedItemsValue.Contains(x.Value));

                foreach(ListItem item inlistItems)
                {
                    item.Selected = true;
                }
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    protectedvoidPage_PreRender(object sender, System.EventArgs e)
    {
        try
        {
            //Registering the scripts file used by the user control. Alternatively you can also set these files inside your master page or the web page on which you are going to use it.
            ScriptManager.RegisterClientScriptInclude(this, this.GetType(), "bootStrapJs", ResolveUrl("~/Scripts/bootstrap.min.js"));
            ScriptManager.RegisterClientScriptInclude(this, this.GetType(), "bootStrapMultiSelectJs", ResolveUrl("~/Scripts/bootstrap-multiselect.js"));
            ScriptManager.RegisterClientScriptInclude(this, this.GetType(), "autoCompleteDdlJs", ResolveUrl("~/Scripts/app/AutoCompleteDdl.js"));
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    protectedvoid ddlAutoCompleteSelect_SelectedIndexChanged1(object sender, EventArgs e)
    {
        if (SelectedIndexChanged != null)
        {
            SelectedIndexChanged(sender, e);
        }
    }

    #endregion

}

AutoCompleteDdl.js

/*Global Variables Declaration*/

//Property Controls
varhdnButtonWidth = '';
varhdnNonSelectedText = '';
varhdnIncludeSelectAllOption = '';
varhdnSelectAllText = '';
varhdnEnableFiltering = '';
varhdnEnableFilteringIgnoreCase = '';
varhdnDisableIfEmpty = '';
varhdnMaxHeight = '';
varhdnFilterPlaceholder = '';
varhdnAllSelectedText = '';
varhdnSelectionMode = '';
//For getting the postBack element ID
varpostBackElementID = '';

//User Control Specific Controls
varlabelId = '';
varhdnTextId = '';
varhdnValueId = '';
varucParentDiv = '';

//Helper variables
varselectedItemsText = '';
varselectedItemsValue = '';

/*This function is used for converting string
"true" or "false" values to Javascript Boolean values.*/
functionconvertToBoolean(value)
{
    return (value === "true");
}

functionpageLoad()
{

    $(document).ready(function()
    {

        Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(InitializeRequestHandler);
        functionInitializeRequestHandler(sender, args)
        {
            postBackElementID = args.get_postBackElement().id;
        }

        //getting the prototype of bootstrap MultiSelect Function/Constructor.
        varmultiSelectFunction = $.fn.multiselect.Constructor;

        //overriding the UpdateButtonText function of bootstrap MultiSelect Function/Constructor.
        multiSelectFunction.prototype.updateButtonText = function() {
            //resetting the variable values to ''
            selectedItemsText = '';
            selectedItemsValue = '';

            //retrieving the selected options
            var options = this.getSelected();

            varinputType = this.options.multiple ? "checkbox" : "radio";

            // resetting the updateButtonText event values
            if (this.options.enableHTML)
            {
                $('.multiselect .multiselect-selected-text', this.$container).html(hdnNonSelectedText);
            }
            else
            {
                $('.multiselect .multiselect-selected-text', this.$container).text(hdnNonSelectedText);
            }

            //retrieving the container parent element i.e. User Control's Parent Div
            ucParentDiv = this.$container.parent();

            //Setting the title attribute of the MultiSelect Button ToNonSelectedText value.
            $('.multiselect', this.$container).attr('title', hdnNonSelectedText);

            //Setting the label value Or ButtonTextvalue(incase of RadioButton) only if the selectedOption Length > 0
            if (options.length > 0)
            {
                if (inputType === "checkbox")
                {
                    varliSelectedItems = this.options.buttonText(options, this.$select);

                    //Finding elements for that specific user control scope(if multiple instances of the same UC exists on the page)
                    labelId = $(ucParentDiv).find("[id*='lblSelectedItems']");
                    hdnTextId = $(ucParentDiv).find("[id*='hdnText']");
                    hdnValueId = $(ucParentDiv).find("[id*='hdnValue']");

                    //Setting the display CSS property value to ""
                    $(labelId).css("display", "");
                    //setting the Label data by forming a unordered list.
                    $(labelId).html("<ul>" + liSelectedItems + "</ul>");

                    //iterating over the selected options and appending it to the variables if the inputType is "checkbox"
                    $.each(options, function(index, option)
                    {
                        selectedItemsText += option.text + ",";
                        selectedItemsValue += option.value + ",";
                    });

                    //removing the last comma from the string value.
                    selectedItemsText = selectedItemsText.substring(0, selectedItemsText.lastIndexOf(","));
                    selectedItemsValue = selectedItemsValue.substring(0, selectedItemsValue.lastIndexOf(","));

                }
                else
                {
                    //Retrieving the selectedOption from the DropDownList. Here we can simply get the text of the SelectedItem by using options.text() function but, it is a standard followed by
                    //Bootstrap Multiselect to call the buttonText function and get the selected Item Text.
                    varselectedOption = this.options.buttonText(options, this.$select);
                    //setting the selected value on Button Title when the SelectionMode is Single.
                    if (this.options.enableHTML)
                    {
                        $('.multiselect .multiselect-selected-text', this.$container).html(selectedOption);
                    }
                    else
                    {
                        $('.multiselect .multiselect-selected-text', this.$container).text(selectedOption);
                    }

                    $('.multiselect', this.$container).attr('title', selectedOption);

                    labelId = $(ucParentDiv).find("[id*='lblSelectedItems']");
                    hdnTextId = $(ucParentDiv).find("[id*='hdnText']");
                    hdnValueId = $(ucParentDiv).find("[id*='hdnValue']");

                    //resetting the label value to ""
                    $(labelId).html("");
                    //Setting the display css property value to "none".
                    $(labelId).css("display", "none");

                    selectedItemsText = options.text();
                    selectedItemsValue = options.val();
                }
            }

            //finally storing the value to the respective hidden fields.
            $(hdnTextId).val(selectedItemsText);
            $(hdnValueId).val(selectedItemsValue);
        }


        //Iterating over each DropdownList on which we need to bind our Bootstrap MultiSelect.
        $("select[id*='ddlAutoCompleteSelect']").each(function()
        {
            varddlCntrl = $(this);
            //retrieving the parent element of the dropdownlist control.
            vardivUCParent = $(ddlCntrl).parent();

            //retrieving the values of the hidden fields/ property values
            hdnButtonWidth = $("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnButtonWidth")).val();
            hdnNonSelectedText = $("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnNonSelectedText")).val();
            hdnIncludeSelectAllOption = convertToBoolean($("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnIncludeSelectAllOption")).val().toString().toLowerCase());
            hdnSelectAllText = $("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnSelectAllText")).val();
            hdnEnableFiltering = convertToBoolean($("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnEnableFiltering")).val().toString().toLowerCase());
            hdnEnableFilteringIgnoreCase = convertToBoolean($("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnEnableFilteringIgnoreCase")).val().toString().toLowerCase());
            hdnDisableIfEmpty = convertToBoolean($("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnDisableIfEmpty")).val().toString().toLowerCase());
            hdnMaxHeight = $("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnMaxHeight")).val();
            hdnFilterPlaceholder = $("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnFilterPlaceholder")).val();
            hdnAllSelectedText = $("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnAllSelectedText")).val();
            hdnSelectionMode = $("#" + ddlCntrl.attr("id").replace("ddlAutoCompleteSelect", "hdnSelectionMode")).val();

            //Retrieving the SelectionMode property value.
            varinputType = hdnSelectionMode;

            //Applying Bootstrap MultiSelect on DropDownList.
            $(this).multiselect({
                buttonWidth: hdnButtonWidth,
                includeSelectAllOption: hdnIncludeSelectAllOption,
                enableFiltering: hdnEnableFiltering,
                enableCaseInsensitiveFiltering: hdnEnableFilteringIgnoreCase,
                selectAllText: hdnSelectAllText,
                nonSelectedText: hdnNonSelectedText,
                disableIfEmpty: hdnDisableIfEmpty,
                maxHeight: hdnMaxHeight,
                filterPlaceholder: hdnFilterPlaceholder,
                allSelectedText: hdnAllSelectedText,
                buttonText: function(options, select)
                {
                    if (options.length === 0)
                    {
                        returnthis.nonSelectedText;
                    }
                    else
                    {
                        var selected = '';
                        //For fetching the selected option if the SelectionMode for Dropdownlist is Multiple. i,e. Checkbox.
                        if (inputType === "checkbox")
                        {
                            options.each(function()
                            {
                                var label = ($(this).attr('label') !== undefined) ? $(this).attr('label') : $(this).text();
                                selected += "<li>" + label + "</li>";
                            });
                        }
                        else
                        {
                            //For retrieving the selected option text if the SelectionMode for Dropdownlist is Single. i.e. RadioButton
                            selected = options.text();
                        }
                        return selected;
                    }
                }
            });

            //For keeping the current dropdownlist open after postback
            if (inputType === "checkbox")
            {
                if (postBackElementID == $(this).attr("id"))
                {
                    //finding the div with class .btn-group
                    vardivButtonGroup = $("#" + divUCParent.attr("id")).find(".btn-group");
                    $(divButtonGroup).addClass("open");
                }
            }
        });
    });
}

Default.aspx

<%@PageLanguage="C#"AutoEventWireup="true"CodeFile="Default.aspx.cs"Inherits="_Default"%><%@RegisterSrc="~/UserControl/AutoCompleteDdl.ascx"TagName="AutoCompleteDdl"TagPrefix="uc1"%>
<!DOCTYPEhtml>
<html
    xmlns="http://www.w3.org/1999/xhtml">
    <headrunatheadrunat="server">
        <title>Bootstrap Multiselect</title>
        <linkrellinkrel="stylesheet"type="text/css"href="http://netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css"/>
        <linkrellinkrel="stylesheet"type="text/css"href="Style/bootstrap-multiselect.css"/>
        <scripttypescripttype="text/javascript"src="Scripts/jquery-1.9.1.min.js">
        </script>
    </head>
    <body>
        <formidformid="form1"runat="server">
            <asp:ScriptManagerIDasp:ScriptManagerID="ScriptManager1"runat="server">
            </asp:ScriptManager>
            <asp:UpdatePanelIDasp:UpdatePanelID="udpMain"runat="server">
                <ContentTemplate>
                    <divclassdivclass="container">
                        <divclassdivclass="row">
                            <divclassdivclass="col-md-12">
                                <h3>Bootstrap MultiSelectDropdownlist</h3>
                                <table>
                                    <tbody>
                                        <tr>
                                            <tdcolspantdcolspan="2">
                                                <h4>Single Select Option</h4>
                                            </td>
                                        </tr>
                                        <tr>
                                            <tdvaligntdvalign="top">Select Item:
                                            </td>
                                            <td>
                                                <uc1:AutoCompleteDdlIDuc1:AutoCompleteDdlID="ddlSingleSelect"runat="server"IncludeSelectAllOption="false"
AutoPostBack="true"ButtonWidth="320px"SelectAllText="All"NonSelectedText="--Select Option--"
MaxHeight="400"EnableFiltering="true"FilterPlaceholder="Search For Something..."
SelectionMode="Single"PlaceHolder="Select a Keyword"/>
                                                <p>
                                                    <asp:ButtonIDasp:ButtonID="btnSingleSelect"runat="server"Text="Get Data"OnClick="btnSingleSelect_Click"/>
                                                </p>
                                            </td>
                                        </tr>
                                        <tr>
                                            <tdcolspantdcolspan="2">
                                                <asp:LabelIDasp:LabelID="lblSingleSelectData"runat="server"/>
                                            </td>
                                        </tr>
                                    </tbody>
                                </table>
                            </div>
                        </div>
                        <divclassdivclass="row">
                            <divclassdivclass="col-md-12">
                                <table>
                                    <tbody>
                                        <tr>
                                            <tdcolspantdcolspan="2">
                                                <h4>Multi Select WithAutoPostBack</h4>
                                            </td>
                                        </tr>
                                        <tr>
                                            <tdvaligntdvalign="top">Select Item:
                                            </td>
                                            <td>
                                                <uc1:AutoCompleteDdlIDuc1:AutoCompleteDdlID="ddlMultiSelect"runat="server"IncludeSelectAllOption="false"
AutoPostBack="true"ButtonWidth="320px"SelectAllText="All"NonSelectedText="--Select Option--"
MaxHeight="400"EnableFiltering="true"FilterPlaceholder="Search For Something..."
SelectionMode="Multiple"PlaceHolder="Select a Keyword"/>
                                                <p>
                                                    <asp:ButtonIDasp:ButtonID="btnMultiSelect"runat="server"Text="Get Data"OnClick="btnMultiSelect_Click"/>
                                                </p>
                                            </td>
                                        </tr>
                                        <tr>
                                            <tdcolspantdcolspan="2">
                                                <asp:LabelIDasp:LabelID="lblMultiSelectData"runat="server"/>
                                            </td>
                                        </tr>
                                    </tbody>
                                </table>
                            </div>
                        </div>
                        <divclassdivclass="row">
                            <divclassdivclass="col-md-12">
                                <table>
                                    <tbody>
                                        <tr>
                                            <tdcolspantdcolspan="2">
                                                <h4>Multi Select With AutoPostback And Dependent DDL</h4>
                                            </td>
                                        </tr>
                                        <tr>
                                            <tdvaligntdvalign="top">Select Item:
                                            </td>
                                            <td>
                                                <uc1:AutoCompleteDdlIDuc1:AutoCompleteDdlID="ddlPrimaryMultiSelect"runat="server"IncludeSelectAllOption="false"
AutoPostBack="true"ButtonWidth="320px"SelectAllText="All"NonSelectedText="--Select Option--"
MaxHeight="400"EnableFiltering="true"FilterPlaceholder="Search For Something..."
SelectionMode="Single"PlaceHolder="Select a Keyword"/>
                                            </td>
                                        </tr>
                                        <tr>
                                            <td>Select Another Item:</td>
                                            <td>
                                                <asp:DropDownListIDasp:DropDownListID="ddlDependent"runat="server"CssClass="dropdown">
                                                </asp:DropDownList>
                                            </td>
                                        </tr>
                                        <tr>
                                            <tdcolspantdcolspan="2">
                                                <asp:LabelIDasp:LabelID="lblMultiPostbckData"runat="server"/>
                                            </td>
                                        </tr>
                                    </tbody>
                                </table>
                            </div>
                        </div>
                    </div>
                </ContentTemplate>
            </asp:UpdatePanel>
        </form>
    </body>
</html>

Default.aspx.cs

using System;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Web;
usingSystem.Web.UI;
usingSystem.Web.UI.WebControls;

publicpartialclass_Default: System.Web.UI.Page
{
    List < SelectModel > lstData = newList < SelectModel > ();
    List < SelectModel > lstDependent = newList < SelectModel > ();

    protectedvoidPage_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            LoadData();
            LoadSingleSelectData();
            LoadMultiSelectData();
            LoadPrimaryMultiSelect();
        }
        ddlPrimaryMultiSelect.SelectedIndexChanged += ddlPrimaryMultiSelect_SelectedIndexChanged;
    }

    publicvoidddlPrimaryMultiSelect_SelectedIndexChanged(object sender, EventArgs e) {
        LoadDependentDDL();
    }

    privatevoidLoadData()
    {
        for (inti = 0; i < 5; i++)
        {
            lstData.Add(newSelectModel()
            {
                Value = "Item " + i, Text = "Item " + i
            });
        }
    }

    privatevoidLoadSingleSelectData()
    {
        ddlSingleSelect.DataValueField = "Value";
        ddlSingleSelect.DataTextField = "Text";
        //Setting the data source for the dropdownlist
        ddlSingleSelect.DataSource = lstData;
    }

    privatevoidLoadMultiSelectData()
    {
        ddlMultiSelect.DataValueField = "Value";
        ddlMultiSelect.DataTextField = "Text";
        ddlMultiSelect.DataSource = lstData;
    }

    privatevoidLoadPrimaryMultiSelect()
    {
        ddlPrimaryMultiSelect.DataValueField = "Value";
        ddlPrimaryMultiSelect.DataTextField = "Text";
        ddlPrimaryMultiSelect.DataSource = lstData;
    }

    privatevoidLoadDependentDDL()
    {
        stringselectedItem = ddlPrimaryMultiSelect.SelectedItem.Text;
        stringsubItem = "Sub " + selectedItem;
        lstDependent.Clear();
        lstDependent.Add(newSelectModel()
        {
            Text = subItem, Value = subItem
        });
        ddlDependent.DataValueField = "Value";
        ddlDependent.DataTextField = "Text";
        ddlDependent.DataSource = lstDependent;
        ddlDependent.DataBind();
    }

    protectedvoidbtnSingleSelect_Click(object sender, EventArgs e) {
        string value = ddlSingleSelect.Value;
        string text = ddlSingleSelect.Text;

        lblSingleSelectData.Text = "<b>Value: </b>" + value + "<br/><b>Text: </b>" + text;
    }

    protectedvoidbtnMultiSelect_Click(object sender, EventArgs e)
    {
        string value = ddlMultiSelect.Value;
        string text = ddlMultiSelect.Text;

        lblMultiSelectData.Text = "<b>Value: </b>" + value + "<br/><b>Text: </b>" + text;
    }

}

Now let’s run the application and you’ll see the following output.

Figure 1: Output