显示的数据，小数点后保留2位

 <asp:GridView ID="gvPartDetail" runat="server" AutoGenerateColumns="False" CellPadding="4"
                                    Font-Names="Arial" Font-Size="10pt" AllowPaging="False" Style="text-align: center; font-size: xx-small;"
                                    OnRowDataBound="gvPartDetail_RowDataBound">
                                    <PagerSettings Position="Bottom" Visible="False" />
                                    <Columns>
                                        <asp:BoundField HeaderText="Plant_Id" DataField="Plant_Id" />

                                        <asp:BoundField HeaderText="Test Date" DataField="test_date" />
                                        <asp:BoundField HeaderText="Yield Str" DataField="yield_strength_long_front" DataFormatString="{0:F}"/>
                                        <asp:BoundField HeaderText="Yield Str T6" DataField="yield_strength_T6" DataFormatString="{0:F}"/>
                                        <asp:BoundField HeaderText="Tensile Str" DataField="tensile_strength_long_front" DataFormatString="{0:F}"/>
                                        <asp:BoundField HeaderText="Uniform Elong%" DataField="uni_elongation_long_front" DataFormatString="{0:F}"/>
                                        <asp:BoundField HeaderText="Total Elong T6%" DataField="te_percent_t6" DataFormatString="{0:F}"/>
                                    </Columns>
                                </asp:GridView>

 protected string GetByViewState_Point2(object data)
    {
        if (data != DBNull.Value && data!=null)
        {
            var newData = Convert.ToDouble(data).ToString("f2");
            return newData;
        }
        return string.Empty;
    }