I ran across an issue today where my data format string was not being applied to my data in a gridview.  It worked locally, but not in dev or test.  Here's what I had:

<asp:BoundField DataField="GrandTotal" HeaderText="Grand Total" ReadOnly="True" SortExpression="GrandTotal" DataFormatString="{0:c}" />

Ok what would make this render differently in dev?  I looked at the HtmlEncodeFormatString property of the BoundField, noticing that setting it to false made the formatting go away locally as well.  So I assumed that I needed to add HtmlEncodeFormatString="true" in dev to make it work.  However, I got the following error message:

Error: Type 'System.Web.UI.WebControls.BoundField' does not have a public property named 'HtmlEncodeFormatString'.

No idea why this is happening.  I googled the error but found nothing useful.  There is an issue with ASP.NET 3.5 and this property defaulting to true, but I don't have 3.5 installed on the dev box.  So that can't be it.

So I had the bright idea to convert this BoundField to a template column (by clicking the linkbutton in the Edit Columns designer).  I got this:

<asp:TemplateField HeaderText="Grand Total" SortExpression="GrandTotal">

  <ItemTemplate>

    <asp:Label ID="Label1" runat="server" Text='<%# Bind("GrandTotal", "{0:c}") %>'></asp:Label>

  </ItemTemplate>

</asp:TemplateField>

Magically, this works both locally and in dev.  I have no idea why.