Interoperability between .NET, Java and legacy stacks

Most cross-vendor failures come from a handful of known divergences in encoding, dates, nulls and empty collections.

The known divergences

Area	The disagreement	Fix
Encoding style	One side emits RPC/encoded	Force document/literal wrapped
Empty array	One emits no element, the other an empty element	Agree on `minOccurs=0` and treat both as empty
Null value	`xsi:nil` versus an omitted element	Use `nillable="true"` consistently, or omit consistently
Date and time	Local time without an offset	Require an offset in the schema pattern
Decimal rounding	Different default scale in serialisation	Pin the scale with `xs:fractionDigits`
Boolean	`1` versus `true`	Both are valid; make the parser accept both
Namespace prefix	`ns1:` versus `tns:`	Never compare XML as text; parse it
Header ordering	Different order of header blocks	Compare headers by name, not position
WS-Security canonicalisation	Inclusive versus exclusive	Pin exclusive canonicalisation with comments off

<!-- A conformance harness: assert on the parsed tree, never on the string -->
<!-- tools/compare.xsl -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="text"/>
  <xsl:template match="/">
    <xsl:for-each select="//*">
      <xsl:value-of select="local-name()"/>
      <xsl:text> </xsl:text>
      <xsl:value-of select="normalize-space(.)"/>
      <xsl:text>&#10;</xsl:text>
    </xsl:for-each>
  </xsl:template>
</xsl:stylesheet>

# Normalise both responses and diff them
xsltproc tools/compare.xsl java-response.xml > java.txt
xsltproc tools/compare.xsl dotnet-response.xml > dotnet.txt
diff -u java.txt dotnet.txt

Running a cross-stack conformance suite

Generate clients for all stacks from the same WSDL revision, and record which revision each was built from.
Run a shared request fixture set through every client and diff the normalised responses.
Include the negative cases: a missing optional field, a maximum-length string, a decimal with a trailing zero, a timestamp at midnight UTC, and a deliberate fault.
Test with the oldest runtime you still support. Modern stacks are more forgiving than the legacy partner you will actually meet.
Review the WS-I Basic Profile for the rules your platform violates by default, then disable those violations explicitly.
Version the WSDL and the harness together so a contract change fails the suite rather than a production partner.

⚠️

Do not compare SOAP responses as strings. Namespace prefix choice, attribute order, self-closing tags and insignificant whitespace all vary legitimately between stacks, and a string diff will report dozens of failures that are not defects.

FAQ

Can I ever compare responses byte for byte?

Only for signature verification, and then both sides must canonicalise identically by agreement. For functional comparison, parse and normalise.

Why does the .NET client reject a valid Java response?

Usually a schema element the .NET proxy generated as non-nillable, or an empty element where the client expects an omitted one. Compare the generated proxy's schema against the WSDL.

XML Schema and data types in messages Attachments and binary data: MTOM and SwA

Last refreshed 2026-09-18.

Interoperability between .NET, Java and legacy stacks

The known divergences

Running a cross-stack conformance suite

FAQ

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