CSS For Ajax ComboBox

Question

This my Css For ComboBox

 

<ajaxToolkit:ComboBox ID="cmbSname" runat="server"
                           AutoCompleteMode="SuggestAppend" CssClass="WindowsStyle"
                           DropDownStyle="DropDownList" AutoPostBack="True"
                           onselectedindexchanged="cmbSname_SelectedIndexChanged"></ajaxToolkit:ComboBox>
                       <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager>

.WindowsStyle .ajax__combobox_inputcontainer .ajax__combobox_textboxcontainer input
  {
      margin: 0;
      border: solid 1px #7F9DB9;
      border-right: 0px none;
      padding: 1px 0px 0px 5px;
      font-size: 13px;
      height: 18px;
      position: relative;
  }
  .WindowsStyle .ajax__combobox_inputcontainer .ajax__combobox_buttoncontainer button
  {
      margin: 0;
      padding: 0;
      background-image: url(windows-arrow.gif);
      background-position: top left;
      border: 0px none;
      height: 21px;
      width: 21px;
  }
  .WindowsStyle .ajax__combobox_itemlist
  {
      border-color: #7F9DB9;
  }

This is My Output

 

But I want This type of Combobox