BizTalk: xpath: How to work with empty and Null elements in the Orchestration

November 17, 2009 · 2 min read

The problem is with the Empty-Null cases in the xpath expressions.

Is it possible to separate all these cases in Expression shapes of the Orchestration xpath?

For example, we have the record with element, in such flavors:

 case: "NonEmpty"

ns0:People\
    ns0:Name\Name_0</ns0:Name>
    ns0:IsDependent\IsDependent_0</ns0:IsDependent>
..

case: "Empty"

  ns0:People\
    ns0:Name\</ns0:Name>
    ns0:IsDependent\IsDependent_0</ns0:IsDependent>
..

 case: "OneTag"

ns0:People\
    ns0:Name/\    ns0:IsDependent\IsDependent_0</ns0:IsDependent>
..

 case: "Null"

ns0:People\
  
    ns0:IsDependent\IsDependent_0</ns0:IsDependent>
..

**Is it possible to separate all these cases in Expression shapes of the Orchestration?
**

There is no information into the MSDN about this [http://msdn.microsoft.com/en-us/library/aa561906(BTS.10).aspx]

I tried to use the xpath() function in two variants, one with "string(xpath_expression)" second with "xpath_expression"

Expression Shape:

[

System.Diagnostics.Trace.WriteLine("== with string() ====================================================================");

var_xpathString = "string(/*[local-name()='Root' and namespace-uri()='http://MapTest.IncPerson'\]/\*\[local-name()='People' and namespace-uri()='http://MapTest.IncPerson'\]/\*\[local-name()='Name' and namespace-uri()='http://MapTest.IncPerson'\])";

System.Diagnostics.Trace.WriteLine("[" + System.Convert.ToString(xpath (msg_SourceRoot, var_xpathString)) + "]");

if ( xpath (msg_SourceRoot, var_xpathString) == null)
    { System.Diagnostics.Trace.WriteLine("Name == null"); } 

else if ( xpath (msg_SourceRoot, var_xpathString) == "")
    { System.Diagnostics.Trace.WriteLine("Name == Empty");}

else
    { System.Diagnostics.Trace.WriteLine("Name != null && Name != Empty"); }

System.Diagnostics.Trace.WriteLine("-- no string() --------------------------------------------------------------------");
var_xpathString = "/*[local-name()='Root' and namespace-uri()='http://MapTest.IncPerson'\]/\*\[local-name()='People' and namespace-uri()='http://MapTest.IncPerson'\]/\*\[local-name()='Name' and namespace-uri()='http://MapTest.IncPerson'\]";

System.Diagnostics.Trace.WriteLine("[" + System.Convert.ToString(xpath (msg_SourceRoot, var_xpathString)) + "]");

if ( xpath (msg_SourceRoot, var_xpathString) == null)
    { System.Diagnostics.Trace.WriteLine("Name == null"); }

else if ( xpath (msg_SourceRoot, var_xpathString) == "")
    { System.Diagnostics.Trace.WriteLine("Name == Empty"); }

else
    { System.Diagnostics.Trace.WriteLine("Name != null && Name != Empty");}

 ]

I.e. the "string(xpath_expression)" expression is used in the firs section, the"xpath_expression" is used  in the second.

Result is:

"NonEmpty" == with string() ====================================================================
[Name_0]
Name != null && Name != Empty
-- no string() --------------------------------------------------------------------
[Microsoft.XLANGs.Core.Part+ArrayBasedXmlNodeList]
Name != null && Name != Empty

"Empty"== with string() ====================================================================
[]
Name == Empty
-- no string() --------------------------------------------------------------------
[Microsoft.XLANGs.Core.Part+ArrayBasedXmlNodeList]
Name != null && Name != Empty

"OneTag"== with string() ====================================================================
[]
Name == Empty
-- no string() --------------------------------------------------------------------
[Microsoft.XLANGs.Core.Part+ArrayBasedXmlNodeList]
Name != null && Name != Empty

"Null"== with string() ====================================================================
[]
Name == Empty
-- no string() --------------------------------------------------------------------
[]
Name == null

Conclusion:

* I cannot separate the cases "Empty" and "OneTag"

* I can separate the cases "Empty and "Null" with "xpath_expression", not with "string(xpath_expression)" expression
* "Null" case does not throw an exception.
* xpath expression inside string() works fine to get all three cases ("Empty", "OneTag", "Null") under one "if" statement. And here it returns only "" (Empty string).

Print | posted on Tuesday, November 17, 2009 3:55 PM

This article is part of the GWB Archives. Original Author: Leonid Ganeline

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