Format String

[c]
String.Format("{0:f2}",value);
String.Format("{0: #,#.00",value);
[/c]
In GridView:
[html]
<%# String.Format("{0:f2}",DataBinder.Eval(Container.DataItem, "pricerange").ToString())%>
[/html]

[html]
<EditItemTemplate>
<asp:TextBox ID="txtPrice" runat="server" Text='<%# String.Format("{0:#,###}",Bind("Price")) %>’ />
</EditItemTemplate>

<EditItemTemplate>
<%# String.Format("{0:C}", Convert.ToString(Eval("Amount")) ) %>
<EditItemTemplate>
[/html]

More info:
http://msdn.microsoft.com/en-us/library/system.string.format.aspx
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.boundfield.dataformatstring.aspx