XmlSerializer: WSDL for XmlAttribute fields does not set use="required" flag

[vidrenning]

The WSDL schema that is generated for fields or properties with the [XmlAttribute] attribute is not correct. It differs from the WSDL that is generated by a ASP.NET ASMX Web Service. Let's take a look at the following class:

public class AttributeType
{
    [XmlAttribute]
    public int IntProperty { get; set; }

    [XmlAttribute]
    public int OptionalIntProperty { get; set; }

    public bool ShouldSerializeOptionalIntProperty()
    {
        return OptionalIntProperty != 0;
    }
}

SoapCore will generate a WSDL, such as the following:

<xsd:attribute name="IntProperty" type="xsd:int" />
<xsd:attribute name="OptionalIntProperty" type="xsd:int" />

However the WSDL that is generated by ASMX Web Services in .NET Framework is different. It adds the use="required" attribute for value types (such as int), to indicate that they are required. The required attribute is added for all value types, except if the class defines a ShouldSerialize*() method, which makes the type optional again.

This is the how the generated WSDL should actually look:

<xsd:attribute name="IntProperty" type="xsd:int" use="required" />
<xsd:attribute name="OptionalIntProperty" type="xsd:int" />

This applies to the current version v1.1.0.42.