<asp:GridView ID="grid_patient" Style="width: 100%;" CssClass="salesGrid" runat="server" GridLines="None" AutoGenerateColumns="False" ProcessFocusedRowChangedOnServer="disable" >

.salesGrid
        {
            font-size: 12px;
            overflow: hidden;
            border:1px solid #000000;
        }

.gridlines table
{
  border-collapse:collapse;
}
.gridlines table tr td
{
 padding:0;
 border:1px solid black;
}