.NET xsd importer creates unserializable class

Question

I am using the .NET XSD.EXE importer to generate C# classes from a collection of XSD files. When I tried to serialize one of the classes to XML it failed (InvalidOperationException), and when I dug into it I discovered it one of the created classes appears to be wrong.

Here is the pertinent XSD code:

<xsd:complexType name="SuccessType">
    <xsd:annotation>
        <xsd:documentation>Indicates in a response message that a request was successfully processed.</xsd:documentation>
    </xsd:annotation>
    <xsd:sequence>
        <xsd:element ref="Warnings" minOccurs="0" maxOccurs="unbounded"/>
    </xsd:sequence>
</xsd:complexType>
<!-- .. snip .. -->
<xsd:element name="Warnings" type="WarningsType">
    <xsd:annotation>
        <xsd:documentation>The processing status of a business message and any related warnings or informational messages.</xsd:documentation>
    </xsd:annotation>
</xsd:element>
<!-- .. snip .. -->
<xsd:complexType name="WarningsType">
    <xsd:annotation>
        <xsd:documentation>A collection of warnings generated by the successful processing of a business message.</xsd:documentation>
    </xsd:annotation>
    <xsd:sequence>
        <xsd:element ref="Warning" maxOccurs="unbounded"/>
    </xsd:sequence>
</xsd:complexType>
<!-- .. snip .. -->
<xsd:element name="Warning" type="WarningType">
    <xsd:annotation>
        <xsd:documentation>Defines details of a warning that occurred during message processing.</xsd:documentation>
    </xsd:annotation>
</xsd:element>
<!-- .. snip .. -->
<xsd:complexType name="WarningType">
    <xsd:annotation>
        <xsd:documentation>Defines details of a warning that occurred during message processing.</xsd:documentation>
    </xsd:annotation>
    <xsd:sequence>
        <xsd:element ref="WarningCategory"/>
        <xsd:element ref="WarningCode"/>
        <xsd:element ref="WarningShortMessage"/>
        <xsd:element ref="WarningMessage"/>
    </xsd:sequence>
</xsd:complexType>

And here is the C# code generated from it:

public partial class SuccessType
{

    private WarningType[][] warningsField;

    /// <remarks/>
    [System.Xml.Serialization.XmlArrayItemAttribute("Warning", typeof(WarningType), IsNullable = false)]
    public WarningType[][] Warnings
    {
        get
        {
            return this.warningsField;
        }
        set
        {
            this.warningsField = value;
        }
    }
}

It made Warnings an array of an array of WarningType. When I attempt to serialize that to XML I get an InvalidOperationException exception:

• Unable to generate a temporary class (result=1).
• error CS0030: Cannot convert type 'WarningType[]' to 'WarningType'
• error CS0030: Cannot convert type 'WarningType[]' to 'WarningType'
• error CS0029: Cannot implicitly convert type 'WarningType' to 'WarningType[]'
• error CS0029: Cannot implicitly convert type 'WarningType' to 'WarningType[]'

But if I change the generated code from WarningType[][] to WarningType[] then it serializes fine.

Short of editing the generated C# class whenever I regenerate this (which hopefully will be less frequently going forward), is there any other solution? Is this a bug in xsd.exe or is the XSD file incorrect? Maybe there is a problem in the XmlSerializer?

What I want is C# code that correctly serializes to XML that validates against the XSD. Right now the jagged array seems to be wrong because if I remove it then it generates the XML.

I am using Visual Studio 2008.

Answer 1

There are bugs in the xsd.exe tool. I don't remember this particular one, but I do remember finding problems with jagged arrays, and it's possible this remains a bug. if you're willing, you could use the XsdObjbectGen tool, also from Microsoft, but released independently and out-of-band from the .NET SDK.

One thing you could do is go the reverse direction: write the C# code, then generate the schema with xsd.exe, and see what is different. It's possible xsd.exe wants the schema to look a particular way, in order to correctly generate correct code for jagged arrays.

---

Actually, upon re-reading your question, you never said what you really wanted. Do you want SuccessType to contain an array-of-arrays, or not?

And is it WarningsType or WarningType? There's some disagreement between the code snips you provided.

---

Assuming you wanted the array-of-arrays, I wrote this C# code:

public class WarningType
{
    public String oof;
}


public partial class SuccessType
{
    private WarningType[][] warningsField;

    /// <remarks/>
    [System.Xml.Serialization.XmlArrayItemAttribute("Warning", typeof(WarningType[]), IsNullable = false)]
    public WarningType[][] Warnings
    {
        get
        {
            return this.warningsField;
        }
        set
        {
            this.warningsField = value;
        }
    }
}

... then compiled it into a DLL. Then I ran xsd.exe on that DLL, and generated this XSD:

<xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="WarningType" nillable="true" type="WarningType" />
  <xs:complexType name="WarningType">
    <xs:sequence>
      <xs:element minOccurs="0" maxOccurs="1" name="oof" type="xs:string" />
    </xs:sequence>
  </xs:complexType>
  <xs:element name="SuccessType" nillable="true" type="SuccessType" />
  <xs:complexType name="SuccessType">
    <xs:sequence>
      <xs:element minOccurs="0" maxOccurs="1" name="Warnings" type="ArrayOfArrayOfWarningType" />
    </xs:sequence>
  </xs:complexType>
  <xs:complexType name="ArrayOfArrayOfWarningType">
    <xs:sequence>
      <xs:element minOccurs="0" maxOccurs="unbounded" name="Warning" type="ArrayOfWarningType" />
    </xs:sequence>
  </xs:complexType>
  <xs:complexType name="ArrayOfWarningType">
    <xs:sequence>
      <xs:element minOccurs="0" maxOccurs="unbounded" name="WarningType" nillable="true" type="WarningType" />
    </xs:sequence>
  </xs:complexType>
</xs:schema>

...and it round-trips. If I then run xsd.exe on that schema, I get a type that wraps an array-of-arrays.