OData 4.0: Referential constraint when principal key is defined in base class

Bernd 0

Hello,

I am implementing an OData v.4.0 web service using the latest version 7.6.4 and I use the Non-Convention model builder to create my EDM model.

I have a base class Person with a Derived class Customer. The Customer class is related to the Order class in a one to many relationship where a customer can have many orders and an order has one customer.

Person

Id : Guid (Key)

Customer : Person

Orders : Collection<Order>

Order

Id : Guid (Key)
Customer : Customer
CustomerId : Guid (Foreign Key)

I create an entity set and entity type for all the types above and I specified the inheritance like this:

customerTypeConfig.DerivesFrom(personTypeConfig);

Key properties are defined in Person and in Order:

entityTypeConfig.HasKey(entityType.GetProperty("Id"));

I also define a navigation property in the Order class and want to set up a referential constraint:

NavigationPropertyConfiguration nav =                                   orderEntityTypeConfig.AddNavigationProperty(customerPropertyInfo, EdmMultiplicity.ZeroOrOne);
orderEntitySetConfig.AddBinding(nav, customerEntitySetConfig);
nav.HasConstraint(customerIdPropertyFromOrderClass, idPropertyFromCustomerClass);

With this setup I get the following exception:

System.ArgumentException: "Cannot redefine property 'Id' already defined on the base type 'Module.BusinessObjects.Person'. It does not matter whether the ReflectedType of the principal PropertyInfo is Customer or Persion - I tried it both ways.

Here is the stack trace:

> Microsoft.AspNet.OData.dll!Microsoft.AspNet.OData.Builder.StructuralTypeConfiguration.ValidatePropertyNotAlreadyDefinedInBaseTypes(System.Reflection.PropertyInfo propertyInfo) Zeile 674 C#

Microsoft.AspNet.OData.dll!Microsoft.AspNet.OData.Builder.StructuralTypeConfiguration.AddProperty(System.Reflection.PropertyInfo propertyInfo) Zeile 309 C#

Microsoft.AspNet.OData.dll!Microsoft.AspNet.OData.Builder.NavigationPropertyConfiguration.HasConstraint(System.Collections.Generic.KeyValuePair<System.Reflection.PropertyInfo, System.Reflection.PropertyInfo> constraint) Zeile 256 C#

Microsoft.AspNet.OData.dll!Microsoft.AspNet.OData.Builder.NavigationPropertyConfiguration.HasConstraint(System.Reflection.PropertyInfo dependentPropertyInfo, System.Reflection.PropertyInfo principalPropertyInfo) Zeile 221 C#

If I just remove the refererential constraint then the model is setup correctly and the service works as expected.

If I remove the inheritance for testing purposes and I define the key in the Customer class instead, then the constraint works fine as well.

How do I define this constraint correctly?

Thanks and regards

Bernd

2 answers

XuDong Peng-MSFT 10,741 Reputation points Microsoft Vendor

2023-02-27T06:24:05.57+00:00
Hi @Bernd,

Based on your description, I'm a little confused about your design.

Order

Id : Guid (Key)

Customer : Customer

CustomerId : Guid (Foreign Key)

As the bold part, you have defined the Customer property in the Order class, but why did you define the CustomerId property again? You can directly get the CustomerId value from the Customer object. But if you define it to do something else, can you clarify more details?

In this case, I think you can use the Customer property in Order class as the navigation property.

Best regards,

Xudong Peng

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Bernd 0 Reputation points

2023-02-27T09:08:46.7366667+00:00

Hello Xudong,

thank you for your answer. The navigation property is created for the Customer property in the Order class.

I implemented CustomerId specifically to make the constraint work. The property is defined as:
public Guid CustomerId { get { return Customer.Id } }

With the help of that property I can then specifiy the constraint between CustumerId in the Order class and the Id property in the Customer class:

navPropertyDefinedInOrderClassForCustomerProperty.HasConstraint(customerIdPropertyInfoInOrderClass, idPropertyInfoInCustomerClass)

To be honest, I don't know how to define the constraint otherwise. I think both property info instances have to be of the same reflected type, that is, Guid in my case.

Here is an example from the Microsoft documentation that I used to implement my service:

https://video2.skills-academy.com/en-us/odata/webapi/referential-constraint

As you see in the Order class there, it not only contains a property of type Customer, but also the CustomerId.

Best regards

Bernd

Bernd 0 Reputation points

2023-02-27T09:46:00.85+00:00

Sorry for the double post.

XuDong Peng-MSFT 10,741 Reputation points Microsoft Vendor

2023-02-27T11:13:55.8+00:00

Hi @Bernd,

Thanks for your reply, it looks like I misunderstood the question a bit.

Based on the doc you mentioned, I found this section in the document. It's consistent with method 1 you mentioned in your problem description: remove the refererential constraint.

Because if user doesn’t add any referential constraint, Web API will try to help user to discovery the foreign key automatically, just like Customer type name "Customer" plus key name "Id" equals the property "CustomerId" in the Order.

So I think you don't have to worry about this, or do you have other designs or needs?

Bernd 0 Reputation points

2023-02-28T15:27:47.9733333+00:00

Hi XuDong,

I think the section you referred to only applies when using the Convention Model Builder. I am doing it programatically, so I think this section applies: https://video2.skills-academy.com/en-us/odata/webapi/referential-constraint#define-referential-constraint-programmatically.

The issue that I have is this: If I implement the referential constraint as described in the documention it works.

But my use case is slightly different:

Class Customer derives from class Person: customerTypeConfig.DerivesFrom(personTypeConfig)

In an EDM model, only one key is allowed in an inheritance structure, so the key is defined in the class Person and not in the class Customer (as it is in the example)

Basically I am using these two features together

Referential Constraint: https://video2.skills-academy.com/en-us/odata/webapi/referential-constraint#define-referential-constraint-programmatically

Derived Complex Type: https://video2.skills-academy.com/en-us/odata/webapi/model-builder-nonconvention#derived-complex-type

With this setup I get the Exception mentioned in my first post.

XuDong Peng-MSFT 10,741 Reputation points Microsoft Vendor

2023-03-01T09:18:46+00:00

Hi @Bernd,

Well, if possible, can you provide a complete code sample so that we can reproduce the issue? Because I'm not sure how your Edm model are defined.

And I found the relevant documentation section below, does this match your current situation?

Type Inheritance Identify Convention- Rule: Only derived types can be walked.

Bernd 0 Reputation points

2023-05-23T10:06:04.61+00:00

Hello XuDong,

thanks for your answer and sorry for the late response. I created a demo project that causes the exception:

System.ArgumentException: "Cannot redefine property 'Id' already defined on the base type 'ODataTest.Models.Person'. Parametername: propertyInfo"

In the demo project, I implemented the odata model twice, once using the convention model builder and then again using the non convention model builder.

When using the convention model builder, the model is created exactly as I want it to be. The metadata looks as follows:

<edmx:Edmx xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx" Version="4.0"> <edmx:DataServices> <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="ODataTest.Models"> <EntityType Name="Order"> <Key> <PropertyRef Name="Id"/> </Key> <Property Name="Id" Type="Edm.Int32" Nullable="false"/> <Property Name="CustomerId" Type="Edm.Int32"/> <NavigationProperty Name="Customer" Type="ODataTest.Models.Customer"> <ReferentialConstraint Property="CustomerId" ReferencedProperty="Id"/> </NavigationProperty> </EntityType> <EntityType Name="Person" Abstract="true"> <Key> <PropertyRef Name="Id"/> </Key> <Property Name="Id" Type="Edm.Int32" Nullable="false"/> <NavigationProperty Name="Assets" Type="Collection(ODataTest.Models.Asset)"/> </EntityType> <EntityType Name="Customer" BaseType="ODataTest.Models.Person"> <Property Name="Name" Type="Edm.String"/> <NavigationProperty Name="Orders" Type="Collection(ODataTest.Models.Order)"/> </EntityType> <EntityType Name="Asset"> <Key> <PropertyRef Name="Id"/> </Key> <Property Name="Id" Type="Edm.Int32" Nullable="false"/> <Property Name="PersonId" Type="Edm.Int32"/> <NavigationProperty Name="Person" Type="ODataTest.Models.Person"> <ReferentialConstraint Property="PersonId" ReferencedProperty="Id"/> </NavigationProperty> </EntityType> </Schema> <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="Default"> <EntityContainer Name="Container"> <EntitySet Name="Person" EntityType="ODataTest.Models.Order"> <NavigationPropertyBinding Path="Customer" Target="Customer"/> </EntitySet> <EntitySet Name="Customer" EntityType="ODataTest.Models.Customer"/> <EntitySet Name="Asset" EntityType="ODataTest.Models.Order"> <NavigationPropertyBinding Path="Customer" Target="Customer"/> </EntitySet> <EntitySet Name="Order" EntityType="ODataTest.Models.Order"> <NavigationPropertyBinding Path="Customer" Target="Customer"/> </EntitySet> </EntityContainer> </Schema> </edmx:DataServices> </edmx:Edmx>

In the second implementation, I try to recreate this model by using the non convention model builder. The problem arises when I try create the constraint for the navigation property in the 'Order' class.

Sadly, I cannot use the convention model builder. Do you have an idea what I am doing wrong?

Here is the link to my demo project: https://acloud.audimex.com/index.php/s/K9nyEtDYGL6erm7

Thanks and regards

Bernd

Bernd 0 Reputation points

2023-05-30T07:37:58.1633333+00:00

For completeness, here is the code from the demo project that creates the odata model:

public static class WebApiConfig { public static void Register(HttpConfiguration config) { //var builder = GetODataConventionModelBuilder(); // <- This works and creates the metada model as expected. var builder = GetODataModelBuilder(); // <- Throws an exception. // My goal is to create the same metadata model as above, but manually // because in my real project I am creating the odata metadata model via reflection. config.MapODataServiceRoute("ODataRoute", null, builder.GetEdmModel()); } public static ODataModelBuilder GetODataConventionModelBuilder() { var builder = new ODataConventionModelBuilder(); builder.EntitySet<Order>("Person"); builder.EntitySet<Customer>("Customer"); builder.EntitySet<Order>("Asset"); builder.EntitySet<Order>("Order"); return builder; } public static ODataModelBuilder GetODataModelBuilder() { var builder = new ODataModelBuilder(); // Person EntityTypeConfiguration personType = builder.AddEntityType(typeof(Person)); EntitySetConfiguration personSet = builder.AddEntitySet("Person", personType); personType.IsAbstract = true; personType.HasKey(typeof(Person).GetProperty("Id")); // Customer EntityTypeConfiguration customerType = builder.AddEntityType(typeof(Customer)); EntitySetConfiguration customerSet = builder.AddEntitySet("Customer", customerType); customerType.DerivesFrom(personType); customerType.AddProperty(typeof(Customer).GetProperty("Name")); // Order EntityTypeConfiguration orderType = builder.AddEntityType(typeof(Order)); EntitySetConfiguration orderSet = builder.AddEntitySet("Order", orderType); orderType.HasKey(typeof(Order).GetProperty("Id")); orderType.AddProperty(typeof(Order).GetProperty("CustomerId")); NavigationPropertyConfiguration orderNav = orderType.AddNavigationProperty(typeof(Order).GetProperty("Customer"), Microsoft.OData.Edm.EdmMultiplicity.ZeroOrOne); orderSet.AddBinding(orderNav, customerSet); // Creating this constraint throws an exception. What am I doing wrong? orderNav.HasConstraint(typeof(Order).GetProperty("CustomerId"), typeof(Customer).GetProperty("Id")); return builder; } }

Best regards

Bernd
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Bernd 0 Reputation points

2023-06-15T10:04:02.63+00:00
I was able to solve the issue. The core of the problem arises when trying to setup a contstraint for a navigation property like this:

myNavigationPropertyConfiguration.HasConstraint(myDependantPropertyInfo, myPrincipalPropertyInfo);

This causes an exception, if 'myPrincipalPropertyInfo' (which is the id property) is defined in a base class of the class where the navigation property points to.

Why? The API tries to find the property, and if it does not exist in the exact class, it tries to add a property configuration. Then it checks if the property is already defined in a base class, and if so, the exception occurs.

In my mind, this is a bug in the implementation of 'HasConstraint', which should also check if the property is defined in a base class and if so, not try to add the property.

Solution:

Wait with the definition of the type inheritance of the model until all navigation properties and constraints are defined. Then, remove the properties from the derived class and as a last step, setup the inheritance:

derivedType.RemoveProperty(derivedType.ClrType.GetProperty("MyIdProperty"));
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OData 4.0: Referential constraint when principal key is defined in base class

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