XmlSerializer WSDL for DateTimeOffset invalid

[vidrenning]

Let's say there is a type such as the following:

public class Hello
{
    public DateTimeOffset TimeStamp { get; set; } = DateTimeOffset.Now;
}

SoapCore currently will generate the following WSDL for it:

<xsd:complexType name="Hello">
  <xsd:sequence>
    <xsd:element xmlns:q1="http://schemas.datacontract.org/2004/07/System" minOccurs="1" maxOccurs="1" name="TimeStamp" type="q1:DateTimeOffset"/>
  </xsd:sequence>
</xsd:complexType>

and further below:

<xsd:schema xmlns:tns="http://schemas.datacontract.org/2004/07/System" elementFormDefault="qualified" targetNamespace="http://schemas.datacontract.org/2004/07/System">
  <xsd:import namespace="http://schemas.microsoft.com/2003/10/Serialization/"/>
  <xsd:complexType name="DateTimeOffset">
    <xsd:annotation>
      <xsd:appinfo>
        <IsValueType xmlns="http://schemas.microsoft.com/2003/10/Serialization/">true</IsValueType>
      </xsd:appinfo>
    </xsd:annotation>
    <xsd:sequence>
      <xsd:element minOccurs="1" maxOccurs="1" name="DateTime" type="xsd:dateTime"/>
      <xsd:element minOccurs="1" maxOccurs="1" name="OffsetMinutes" type="xsd:short"/>
    </xsd:sequence>
  </xsd:complexType>
  <xsd:element name="DateTimeOffset" nillable="true" type="tns:DateTimeOffset"/>
</xsd:schema>

This schema corresponds to the XML that the DataContractSerializer generates, but it does not correspond to the XML that the XmlSerializer generates.

The actual SOAP XML that is transferred is the following:

<Hello>
  <TimeStamp>2024-02-08T09:55:41.2527621+01:00</TimeStamp>
</Hello>

As you can see, the XML generated by the XmlSerializer does not correspond to the WSDL that is generated.