"Namespace prefix is not defined" after update from 1.2.0.1 to 1.2.1

[Montellese]

Hi

We have updated SoapCore from 1.2.0.1 to 1.2.1 in one of our services. Now we get the following error when receiving a SOAP request:

2026-03-06 16:52:58.716 [Debug] [SoapCore.SoapEndpointMiddleware] Received SOAP Request for "/" (810 bytes)
2026-03-06 16:52:58.733 [Information] [SoapCore.SoapEndpointMiddleware] Request for operation "tal_serverPortType"."request" received
2026-03-06 16:52:58.744 [Error] [SoapCore.SoapEndpointMiddleware] An error occurred processing the message
System.InvalidOperationException: There is an error in XML document (1, 1).
 ---> System.InvalidOperationException: Namespace prefix 'tal' is not defined.
   at System.Xml.Serialization.XmlSerializationReader.ToXmlQualifiedName(String value, Boolean decodeName)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderrequestRequest.Read76_Request(Boolean isNullable, Boolean checkType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderrequestRequest.Read77_requestRequest(Boolean isNullable, Boolean checkType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderrequestRequest.Read78_request()
   at InvokeStub_XmlSerializationReaderrequestRequest.Read78_request(Object, Object, IntPtr*)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
   --- End of inner exception stack trace ---
   at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events)
   at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader)
   at SoapCore.Serializer.SerializerHelper.DeserializeObject(XmlDictionaryReader xmlReader, Type parameterType, String parameterName, String parameterNs) in /_/src/SoapCore/Serializer/SerializerHelper.cs:line 103
   at SoapCore.Serializer.SerializerHelper.DeserializeInputParameter(XmlDictionaryReader xmlReader, Type parameterType, String parameterName, String parameterNs, ICustomAttributeProvider customAttributeProvider, IEnumerable`1 knownTypes) in /_/src/SoapCore/Serializer/SerializerHelper.cs:line 50
   at SoapCore.SoapEndpointMiddleware`1.ProcessMessage(Message requestMessage, SoapMessageEncoder messageEncoder, IAsyncMessageFilter[] asyncMessageFilters, HttpContext httpContext, IServiceProvider serviceProvider) in /_/src/SoapCore/SoapEndpointMiddleware.cs:line 489
2026-03-06 16:52:58.774 [Error] [SoapCore.SoapEndpointMiddleware] An error occurred processing the message
System.InvalidOperationException: There is an error in XML document (1, 1).
 ---> System.InvalidOperationException: Namespace prefix 'tal' is not defined.
   at System.Xml.Serialization.XmlSerializationReader.ToXmlQualifiedName(String value, Boolean decodeName)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderrequestRequest.Read76_Request(Boolean isNullable, Boolean checkType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderrequestRequest.Read77_requestRequest(Boolean isNullable, Boolean checkType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderrequestRequest.Read78_request()
   at InvokeStub_XmlSerializationReaderrequestRequest.Read78_request(Object, Object, IntPtr*)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
   --- End of inner exception stack trace ---
   at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events)
   at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader)
   at SoapCore.Serializer.SerializerHelper.DeserializeObject(XmlDictionaryReader xmlReader, Type parameterType, String parameterName, String parameterNs) in /_/src/SoapCore/Serializer/SerializerHelper.cs:line 103
   at SoapCore.Serializer.SerializerHelper.DeserializeInputParameter(XmlDictionaryReader xmlReader, Type parameterType, String parameterName, String parameterNs, ICustomAttributeProvider customAttributeProvider, IEnumerable`1 knownTypes) in /_/src/SoapCore/Serializer/SerializerHelper.cs:line 50
   at SoapCore.SoapEndpointMiddleware`1.ProcessMessage(Message requestMessage, SoapMessageEncoder messageEncoder, IAsyncMessageFilter[] asyncMessageFilters, HttpContext httpContext, IServiceProvider serviceProvider) in /_/src/SoapCore/SoapEndpointMiddleware.cs:line 489
   at SoapCore.SoapEndpointMiddleware`1.ProcessOperation(HttpContext httpContext, IServiceProvider serviceProvider) in /_/src/SoapCore/SoapEndpointMiddleware.cs:line 307

This is the SOAP request:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope
	xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
	xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:xsd="http://www.w3.org/2001/XMLSchema"
	xmlns:tal-server="urn:tal_server"
	xmlns:tal-client="urn:tal_client"
	xmlns:tal="urn:tal">
	<SOAP-ENV:Body>
		<tal-server:request>
			<request xsi:type="tal:CreateSession">
				<sessionId></sessionId>
				<requestId>2982441</requestId>
				<version>2.5</version>
				<clientUrl>http://192.168.1.2:7000</clientUrl>
				<properties>
					<name>xxx</name>
					<value>false</value>
				</properties>
			</request>
		</tal-server:request>
	</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

What is the issue with this request and why did it work fine with version 1.2.0.1?
We can't control the sender of the request, so we need to find a way to handle this properly on our side.

Thanks for your help!

[andersjonsson]

Sorry for not responding earlier.
1.2.1.0 introduced major changes to how incoming messages are read.
The entire request is stored, and a new reader is instantiated at the body tag.
This means the reader can't see namespaces declared at the envelope level.

Unfortunately, I don't see myself having time to work on this anytime soon.
However, I can point you in the right direction if you feel like giving a fix a shot.

I think that the easiest fix would be in ParsedMessage.ExtractSoapBody()
If you copy any missing namespace attributes from root to bodyNode before returning, that should fix your issue.

[xeterixon]

Had a similar problem: a client sent a somewhat ill-formated request.
It worked in previous version of SoapCore
I made a fork and fixed my problem as well as this issue.
I don’t really know if things like this should be fixed, since the client is the culprit. Hence no pull-request.
It can be found in my fork, nevertheless.
https://github.com/xeterixon/SoapCore

[andersjonsson]

Had a similar problem: a client sent a somewhat ill-formated request. It worked in previous version of SoapCore I made a fork and fixed my problem as well as this issue. I don’t really know if things like this should be fixed, since the client is the culprit.

I think this issue should be fixed to preserve backwards compatibility. And I believe it's ok to put your body namespaces on the envelope tag, even if it's unusual.

Could you submit a PR?

[xeterixon]

Done, in #1184

[andersjonsson]

Hopefully fixed in v1.2.1.13 (coming to nuget in a few minutes)

[andersjonsson]

Nuget version will take a while longer. Hopefully it will get sorted shortly #913