XML Canonicalization

Question

Hi, I have to canonicalize some XML data, in order to apply a particular digital signature algorithm. I read about SignedXML and XmlDsigC14NTransform classes, I read the http://www.dotnet247.com/247reference/a.aspx?u=http://www.c-sharpcorner.com/Code/2002/Mar/XMLSignatureSL001.asp article too. But I can't find any way to isolate the canonicalization process from the whole process. In my problem, I have to compute a signature (using a MD5) from the concatenation of a key (a customised key, from none of the standard ones) and the canonical representation of a part of an XML blob of data. May someone give me some link or idea ? Thanks.