datetime formating with string.format

I have a table in my SQL DB that is a DateTime table, what I want to do is take the numeric datetime it stores and convert it to a long date (i.e. 12/12/2012 conversts to December 12, 2012). Seaching the forums it looks like the string.format is the way to go and searching for info on that I found http://www.csharp-examples.net/string-format-datetime/ which lists all the different formats but they do not list a formating string to convert to the format I want to use. Does anyone know what format string I would use to convert a numeric date to a long date like I want? And can you show it in a code example because I am not 100% sure I understand the code examples shown on that site.
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