Friday, 24 December 2010

SSIS: Precedence Constraint with XML

I was using an expression for a precedence constraint in a package recently and came across an issue where, although the expression was valid (and correct, honest!!) the package would not proceed.

Essentially, i was testing that a string variable which contained XML from an XML (XSLT) task was not blank/empty:

LEN(@[User::ErrorXML]) > 0
@[User::ErrorXML]) != ""

I can see the variable in the watch list as but neither of these expression options was working. I guess this is down to the fact that you can't execute these functions on XML but i think its a bit confusing. The variable is of type string, so no matter if the SSIS Task outputs XML, i would have thought its type would have been strongly bound to that whats set in the variable. This doesn't appear to be the case as I precedence constraints on other "standard" string variables evaluate successfully.

Just something to keep any eye out for.

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