<asp:TemplateField HeaderText="اليوم">

                             <ItemTemplate>

                                    <asp:Label  ID="Label4" runat="server" Text=`<%#ConvertArDay(Eval("myday").ToString()) %>`></asp:Label>

                                </ItemTemplate>

                                <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="10px" />

                            </asp:TemplateField>

///////////////////////////////////

 protected string ConvertArDay(string dev)

        {  //sunday   saturday monday   tuesday  wednesday thursday  friday

            switch (dev.Trim())

            {

                case "Sunday": return "الاحد";//1

                case "Monday": return "الاثنين";  //2

                case "Tuesday": return "الثلاثاء";//3

                case "Wednesday": return "الاربعاء";//4

                case "Thursday": return "الخميس";//5

                default: return "";

            }

        }