
Follow these steps to create the above multiselect dropdownlist.

SQL Database to Create Above Table:
CREATE TABLE [dbo].[tblCompany](
[Id] [int] IDENTITY(1,1) NOT NULL,
[Name] [nvarchar](50) NULL
) ON [PRIMARY]
GO
SET IDENTITY_INSERT [dbo].[tblCompany] ON
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (1, N'Wipro')
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (2, N'Accenture')
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (3, N'HCL')
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (4, N'Intelegencia')
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (5, N'Nokia')
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (6, N'Samsung')
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (7, N'Matrix')
INSERT [dbo].[tblCompany] ([Id], [Name]) VALUES (8, N'Microsoft')
SET IDENTITY_INSERT [dbo].[tblCompany] OFF
Asp.Net :
<div style="padding: 20px">
Select Company
<asp:ListBox ID="ddlCompany" runat="server" SelectionMode="Multiple"></asp:ListBox>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<link href="http://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.0.3/css/bootstrap.min.css"
rel="stylesheet" type="text/css" />
<script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.0.3/js/bootstrap.min.js"></script>
<link href="http://cdn.rawgit.com/davidstutz/bootstrap-multiselect/master/dist/css/bootstrap-multiselect.css"
rel="stylesheet" type="text/css" />
<script src="http://cdn.rawgit.com/davidstutz/bootstrap-multiselect/master/dist/js/bootstrap-multiselect.js"
type="text/javascript"></script>
<script type="text/javascript">
$(function () {
$('[id*=ddlCompany]').multiselect({
includeSelectAllOption: true
});
});
</script>
</div>
C# :
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
public partial class Default3 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
bindCompany();
}
}
protected void bindCompany()
{
string strConnection = "Data Source=.; uid=sa; pwd=sql;database=company;";
SqlConnection con = new SqlConnection(strConnection);
string com = "Select Id, Name From tblCompany Order By Name";
SqlDataAdapter da = new SqlDataAdapter(com, con);
DataTable dt = new DataTable();
da.Fill(dt);
if (dt.Rows.Count > 0)
{
ddlCompany.DataTextField = dt.Columns["Name"].ToString();
ddlCompany.DataValueField = dt.Columns["id"].ToString();
ddlCompany.DataSource = dt;
ddlCompany.DataBind();
}
}
}