如何使用c＃从xsd文件中提取属性及其数据类型？

Question

我有两种类型的XSD文件。下面是两种类型的XSD

输入1

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="Body">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="value">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="ConcurrencyToken" />
              <xs:element name="Id" type="xs:string" />
              <xs:element name="Location" type="xs:string" />
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
      <xs:attribute name="odata.context" type="xs:string" use="required" />
    </xs:complexType>
  </xs:element>
</xs:schema>

类型2

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="Body">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="ConcurrencyToken" />
        <xs:element name="Id" type="xs:string" />
        <xs:element name="CatalogName" type="xs:string" />
        <xs:element name="SchemaName" type="xs:string" />
        <xs:element name="NameService" type="xs:string" />
      </xs:sequence>
      <xs:attribute name="odata.context" type="xs:string" use="required" />
    </xs:complexType>
  </xs:element>
</xs:schema>

这是我的代码

 public static List<SchemaStructure> XsdNestedParser(string schemaPath)
        {
            List<SchemaStructure> schemaStructList = new List<SchemaStructure>();

            XmlSchema xmlSchema = null;
            using (var reader = new StreamReader(schemaPath))
            {
                xmlSchema = XmlSchema.Read(reader, null);
            }

            XmlSchemaSet schemaSet = new XmlSchemaSet();
            schemaSet.Add(xmlSchema);
            schemaSet.Compile();
            xmlSchema = schemaSet.Schemas().Cast<XmlSchema>().First();
            foreach (XmlSchemaElement element in xmlSchema.Elements.Values)
            {
                XmlSchemaComplexType complexTypeRoot = element.ElementSchemaType as XmlSchemaComplexType;
                XmlSchemaSequence sequenceRoot = complexTypeRoot.ContentTypeParticle as XmlSchemaSequence;
                foreach (object childElement in sequenceRoot.Items)
                {
                    XmlSchemaElement schemaElement = childElement as XmlSchemaElement;
                    XmlSchemaComplexType complexType = schemaElement.ElementSchemaType as XmlSchemaComplexType;
                    XmlSchemaSequence sequence = complexType.ContentTypeParticle as XmlSchemaSequence;
                    if (complexType != null)
                    {
                        for (int i = 0; i < sequence.Items.Count; i++)
                        {
                            XmlSchemaElement child = sequence.Items[i] as XmlSchemaElement;
                            XmlSchemaChoice choice = sequence.Items[i] as XmlSchemaChoice;
                            string propertyName = String.Empty;
                            string dataType = string.Empty;

                            if (child != null)
                            {
                                propertyName = child.Name;
                                dataType = child.SchemaTypeName.Name;
                                SchemaStructure schemaStructure = new SchemaStructure(propertyName, dataType);
                                schemaStructList.Add(schemaStructure);
                            }
                            else
                            {
                                //Here I am getting nullreference exception while parsing type 2,however if it is type 2 it should go to else
                                for (int j = 0; j < choice.Items.Count; j++)
                                {
                                    XmlSchemaElement schemElement = choice.Items[j] as XmlSchemaElement;
                                    propertyName = schemElement.Name;
                                    dataType = schemElement.SchemaTypeName.Name;
                                    SchemaStructure schemaStructure = new SchemaStructure(propertyName, dataType);
                                    schemaStructList.Add(schemaStructure);
                                }
                            }
                        }
                    }
                    else
                    {

                        string propertyName = schemaElement.Name;
                        string dataType = schemaElement.SchemaTypeName.Name;
                        SchemaStructure schemaStructure = new SchemaStructure(propertyName, dataType);
                        schemaStructList.Add(schemaStructure);

                    }
                }
            }

            return schemaStructList;
        }

我能够提取类型1，但是在提取类型2时我得到了Null异常。我做错了什么？

先谢谢