<table width="100%">
                <tr>
                    <td>
                        <asp:DataList ID="DataList1" runat="server" RepeatColumns="2" RepeatDirection="Horizontal"
                            OnItemDataBound="DataList1_ItemDataBound">
                            <ItemTemplate>
                                <asp:RadioButton runat="server" ID="rbtn" GroupName="testGroup" />
                            </ItemTemplate>
                        </asp:DataList>
                    </td>
                </tr>
                <tr>
                    <td>
                        <asp:Button ID="Show" runat="server" Text="show" OnClick="Show_Click" />  <asp:Label
                            ID="lblSelectedNo" runat="server"></asp:Label></td>
                </tr>
                <tr>
                    <td height="5">
                    </td>
                </tr>
</table>

      private static SqlConnection con;
    private static SqlCommand cmd;
     private static DataTable dt = null;
    

   protected void Page_Load(object sender, EventArgs e)
    {       
        if (!IsPostBack)
        {          
                   
            dt = Loaddepartments(); // function to fill datalist from a table   
            DataList1.DataSource = dt;
            DataList1.DataBind();

           
        }
    }

   private DataTable Loaddepartments()
    {

        setConnection();   

        string strsql = "select eno from emp";
        
         DataSet objDs = new DataSet();
        SqlDataAdapter  objDa = new SqlDataAdapter(strsql, con);
        objDa.Fill(objDs, "DATA_TABLE");
        objDa.Dispose();
        return objDs.Tables["DATA_TABLE"];  
    }






 private void setConnection()
    {
        con = new SqlConnection();
        if (con.State == ConnectionState.Closed)
        {
            con = new SqlConnection(ConfigurationManager.AppSettings["connection string"].ToString());
            con.Open();
        }
    }



 protected void DataList1_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        RadioButton rbtnReplyNos = (RadioButton)e.Item.FindControl("rbtn");
        if (e.Item.ItemIndex > -1)
        {

            int iRow = e.Item.ItemIndex;
            rbtnReplyNos.Text = dt.Rows[iRow].ItemArray[0].ToString();
           
           
        }
        string script = "SetUniqueRadioButton('DataList1.*testGroup',this)";   // javaScript for single selection of radiobuttons in datalist
        rbtnReplyNos.Attributes.Add("onclick", script);
    }



  Javascript for single selection:

        	
	function SetUniqueRadioButton(nameregex, current)
{
   re = new RegExp(nameregex);
   for(i = 0; i < document.forms[0].elements.length; i++)
   {
      elm = document.forms[0].elements[i]
      if (elm.type == 'radio')
      {
         if (re.test(elm.name))
         {
            elm.checked = false;
         }
      }
   }
   current.checked = true;
}




protected void Show_Click(object sender, EventArgs e)
    {
        foreach (DataListItem replyNos in DataList1.Items)
        {
            RadioButton rb = (RadioButton)replyNos.FindControl("rbtn");
            rb.ID = replyNos.ToString();
            bool resposse = rb.Checked;
            if (resposse == true)
            {
                lblSelectedNo.Text = rb.Text;               
                DataList1.DataSource = dt;
                DataList1.DataBind();
                return;
            }
        }
    }