Improve support for groups (fix #109)

XmlSchemaClassGenerator/ModelBuilder.cs

@@ -245,7 +245,7 @@ private TypeModel CreateTypeModel(Uri source, XmlSchemaComplexType complexType,
  // If it's a restriction, do not duplicate elements on the derived class, they're already in the base class.
  // See https://msdn.microsoft.com/en-us/library/f3z3wh0y.aspx
  }
- else particle = complexType.ContentTypeParticle;
+ else particle = complexType.Particle ?? complexType.ContentTypeParticle;
 
  var items = GetElements(particle, complexType);
  var properties = CreatePropertiesForElements(source, classModel, particle, items);
@@ -479,6 +479,7 @@ private IEnumerable<PropertyModel> CreatePropertiesForElements(Uri source, TypeM
  {
  var properties = new List<PropertyModel>();
  var order = 0;
+
  foreach (var item in items)
  {
  PropertyModel property = null;
@@ -495,7 +496,8 @@ private IEnumerable<PropertyModel> CreatePropertiesForElements(Uri source, TypeM
  if (elementQualifiedName.IsEmpty)
  {
  // inner type, have to generate a type name
- var typeName = _configuration.NamingProvider.PropertyNameFromElement(typeModel.Name, element.QualifiedName.Name);
+ var typeModelName = particle is XmlSchemaGroupRef groupRef ? groupRef.RefName : typeModel.XmlSchemaName;
+ var typeName = _configuration.NamingProvider.PropertyNameFromElement(typeModelName.Name, element.QualifiedName.Name);
  elementQualifiedName = new XmlQualifiedName(typeName, typeModel.XmlSchemaName.Namespace);
  // try to avoid name clashes
  if (NameExists(elementQualifiedName))