I am having a textbox with textmode=number in html

<asp:TextBox  Font-Bold="True" ForeColor="Blue" runat ="server" ID="txtProjectCost" format="0.###"
                                min="0" TabIndex ="7" Wrap="False" TextMode ="Number"  ></asp:TextBox>

When i set textbox text from code behind it shows decimal value, but it does not show in textbox. I tried combinations

 txtProjectCost.Text = Decimal.Parse(tb.Rows(0).Item(7))

I this also
txtProjectCost.Text = FormatNumber(CDbl(tb.Rows(0).Item(6)), 3)

but No number is displayed in textbox. I want Number to be display in “..nnn.000” format i.e if no decimal number than padding. I want only numbers to be added in textbox.