How can i show the selected items as comma separated in the Multi select dropdown text field in asp.net
<p>In my web application, i am trying to do show the selected items as comma separated in the Multi select drop down text field is it possible to do and how can i do this can any one tell me. sample image is link <a href="http://i.stack.imgur.com/rT12a.png" rel="nofollow">[As Shown in figure]</a></p>

<p>I tried:</p>

<p>.aspx: </p>

<pre><code>&lt;asp:DropDownCheckBoxes ID="dropdown1" runat="server" UseSelectAllNode="true" UseButtons="true" OnSelectedIndexChanged="dropdown1_SelectedIndexChanged" AutoPostBack="true"&gt;&lt;Style DropDownBoxBoxWidth="200"/&gt;&lt;/asp:DropDownCheckBoxes&gt;
</code></pre>

<p>.CS</p>

<pre><code>      public void ddlsbind()
    {
    string str=string.Empty;
                string query = "select distinct col1 from Collection where sample='" + ddl2.SelectedItem.Text.ToString() + "' and col1 IS NOT NULL";            
 SqlCommand cmd = new SqlCommand(query, con);
                DataTable dt = new DataTable();
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(dt);        
                ddlInsurance.DataSource = dt;
                ddlInsurance.DataTextField = "col1";
                ddlInsurance.DataValueField = "col1";
                ddlInsurance.DataBind();
    }
</code></pre>

<p>Can anyone help me to how to do this.<br>
Thank you</p>