UTF-8 with signature?

Few days ago I was at my customer and we witnessed a wired behavior of excel.

We wanted to display data in excel from the web, so that when you click a link excel will open and display some data in it (not within explorer).

Doing this is pretty simple, all we have to do is create a data grid control, bind it to a data source and let it render.

When we want it to open to excel we have to replace the "pre-render" method with this simple code:
Page.Response.Clear();//clear other HTML form response
Page.Response.AddHeader("Content-Disposition", "attachment;filename=StudentsList.xls");//to open in excel
Page.Response.Charset = "65001";//for UTF-8
myDG.RenderControl(writer);//render grid HTML
Page.Response.End();//End response here.

This works great for most cases.

My client had to display some non-English characters that were all UTF8 encoded. When saving the result HMTL in notepad using UTF8 excel was able to display the special chars ok, but when using the code sample above - we got some wrong data.

After googling around for a while i managed to understand that excel must use UTF8 with signature text and i had to add a signature to it.

So - how do I signature my file as UTF8???

Some more googling allowed me to learn that all I needed to do is add these bytes to the start of the file:
0xEF, 0xBB, 0xBF

Using C#, here is the complete and correct way to do this:

Page.Response.Clear();
Page.Response.ContentType = "application/vnd.ms-excel";
Page.Response.AddHeader("Content-Disposition", "attachment;filename=StudentsList.xls");
Page.Response.Charset = "65001";
byte[] b = new byte[] { 0xEF, 0xBB, 0xBF };
Page.Response.BinaryWrite(b);
myDG.RenderControl(writer);
Page.Response.End();

Now everything should be rendered okay and my file is saved with UTF8 with signature!!!

Hooray!

Well, hope this helps, since I didn't manage to find any document that explains this I thought it might help if I publish one...

Peace, Shai.