Base64 encoded string to file
Solution 1:
Try this:
File.WriteAllBytes(@"c:\yourfile", Convert.FromBase64String(yourBase64String));
Solution 2:
As a first pointer, check out MSDN's documentation on the XmlTextreader's ReadBase64 Method... http://msdn.microsoft.com/en-us/library/system.xml.xmltextreader.readbase64.aspx