Just what are the conventions of the ODataConventionModelBuilder?

Question

There are lots of examples of using ODataConventionModelBuilder with simple, contrived models, often just a single class.

But there's nothing that actually explains what the conventions are; how to code a model that complies with convention. There's no official documentation for it.

So what's the convention?

Answer 1

The conventions used in ODataConventionModelBuilder are described here.

As for how to code a model that complies with the conventions, that is pretty straight forward, or rather you don't need to code a model to the conventions at all. The conventions exist to simplify and standardize how an EF model is expressed in an OData Edm Model. If you find yourself manually enabling features, then you might find there is a convention that can automate this process for you. Understanding what the conventions are might help.

Your answer @LukePuplett describes some of the EF Code First conventions, they don't really apply here, not all directly anyway. I don't want to say you were wrong... ;)

The following is derived from the source code for ConventionModelBuilder.

Type and Property Conventions

NOTE: ordering is important here.

• AbstractTypeDiscoveryConvention
  configures all structural types backed by an abstract CLR type as abstract.

• DataContractAttributeEdmTypeConvention
  Configures classes that have the DataContractAttribute to follow DataContract serialization/deserialization rules.

• NotMappedAttributeConvention
  Ignores properties with the NotMappedAttribute from IEdmStructuredType

  • NotMappedAttributeConvention MUST run before EntityKeyConvention, or it will allow Keys to be excluded from the model

• DataMemberAttributeEdmPropertyConvention
  Configures properties that have DataMemberAttribute as optional or required on their edm type.

  • NOTE: This does not explicitly remove properties that have IgnoreDataMemberAttribute, but it will not explicitly add them either

• DerivedTypeConstraintAttributeConvention
  Adds Derived Type Constraints to the Model if required

• RequiredAttributeEdmPropertyConvention
  Marks properties that have RequiredAttribute as non-optional on their edm type.

• DefaultValueAttributeEdmPropertyConvention
  Sets default value for properties that have DefaultValueAttribute

• ConcurrencyCheckAttributeEdmPropertyConvention
  Marks properties that have ConcurrencyCheckAttribute as non-optional on their EDM type.

• TimestampAttributeEdmPropertyConvention
  Annotates a single column in a Type as the Timestamp column, even if multiple columns are annotated with the TimestampAttribute. This is due to a SQL limitation table (the underlying concept this attribute is bounded to) that only supports one row version column per table.

• ColumnAttributeEdmPropertyConvention
  Marks properties that have ColumnAttribute as the target EDM type.

• KeyAttributeEdmPropertyConvention
  Configures properties that have the KeyAttribute as keys in the IEdmEntityType

  • KeyAttributeEdmPropertyConvention MUST run before EntityKeyConvention

• EntityKeyConvention
  This convention configures properties that are named 'ID' (case-insensitive) or {EntityName}+ID (case-insensitive) as the key.

• ComplexTypeAttributeConvention
  Removes primitive properties that are exposed through ComplexType definitions from the IEdmEntityType

  • This MUST run after Key conventions, basically overrules them if there is a ComplexTypeAttribute

• IgnoreDataMemberAttributeEdmPropertyConvention
  Removes properties that have IgnoreDataMemberAttribute from their edm type.

  • If class is a DataContract and DataMemberAttribute is present on this property, then the property will not be removed, DataMemberAttribute takes precedence

• NotFilterableAttributeEdmPropertyConvention
  Configures a column with fluent IsNotFilterable() if it has a NotFilterableAttribute annotation. This will specify that the property cannot be used in the $filter OData query option.

  • This is the same implementation as NonFilterableAttribute and its related NonFilterableAttributeEdmPropertyConvention

• NonFilterableAttributeEdmPropertyConvention
  Configures a column with fluent IsNotFilterable() if it has a NonFilterableAttribute annotation. This will specify that the property cannot be used in the $filter OData query option.

  • This is the same implementation as NotFilterableAttribute and its related NotFilterableAttributeEdmPropertyConvention;

• NotSortableAttributeEdmPropertyConvention
  Configures a column with fluent IsNotSortable() if it has a NotSortableAttribute annotation. This will specify that the property cannot be used in the $orderby OData query option.

• UnsortableAttributeEdmPropertyConvention
  Configures a column with fluent IsNotSortable() if it has a UnsortableAttribute annotation. This will specify that the property cannot be used in the $orderby OData query option.

• NotNavigableAttributeEdmPropertyConvention
  Configures a column with fluent IsNotNavigable() if it has the NotNavigableAttribute annotation. This will specify that the property cannot be navigated in OData query.

  • This does not preclude $expand, it means that the propert cannot be used to traverse to the associated resource using an Entity Path, for instance if ProductType had this attribute, and was a navigation property that returned a ProductType reference, the following OData path would not be servived: ~/api/products(112)/ProductType this is a feature from the updates to support Containment.

• NotExpandableAttributeEdmPropertyConvention
  Configures a column with fluent IsNotExpandable() if it has a NotExpandableAttribute annotation. This will specify that the property cannot be used in the $expand OData query option.

• NotCountableAttributeEdmPropertyConvention
  Configures a column with fluent IsNotCountable() if it has a NotCountableAttribute annotation. This will specify that the $count cannot be applied on the property.

• MediaTypeAttributeConvention
  Configures a class with fluent MediaType() which marks this entity type as media type.

• AutoExpandAttributeEdmPropertyConvention
  Configured the AutoExpand feature of a column when it has the AutoExpandAttribute annotation.

• AutoExpandAttributeEdmTypeConvention
  When AutoExpandAttribute is placed on a class it can specify all navigation properties are auto expanded.

• MaxLengthAttributeEdmPropertyConvention
  Configures string or binary properties that have the MaxLengthAttribute annotation.

• PageAttributeEdmPropertyConvention
  Sets the page size and Max Top of the entity type based on the PageAttribute annotation if present on any of the properties in the class.

  • There is no added value of supporting this on a property level, but it is offered as a redundancy for poorly configured code.

• PageAttributeEdmTypeConvention
  Sets the page size and Max Top of the entity type based on the PageAttribute annotation on the class.

• ExpandAttributeEdmPropertyConvention
  Configures OData $expand query option for navigation columns with ExpandAttribute annotation.

• ExpandAttributeEdmTypeConvention
  Set the ExpandConfigurations of navigation properties of this structural type based on the ExpandAttribute annotation on the class.

• CountAttributeEdmPropertyConvention
  Configures the $count OData query options for specific columns with the CountAttribute annotation. The $count OData query option can be explicity enabled or disabled with the CountAttribute annotation.

• CountAttributeEdmTypeConvention
  Set whether the $count can be applied on the edm type. The $count OData query option can be explicity enabled or disabled with the CountAttribute annotation.

• OrderByAttributeEdmTypeConvention
  Configures the OData $orderby query option settings for a type based on the OrderByAttribute on the class or on the properties. When used on a class, the default $orderby value can be specified. When used on properties it can also prevent that property from being referenced in an $orderby OData query option.

• FilterAttributeEdmTypeConvention
  Configures the OData $filter query option settings for a type based on the FilterAttribute on the class or properties.

• OrderByAttributeEdmPropertyConvention Configures the OData $orderby query option settings for a type based on the OrderByAttribute on the class or on the properties. When used on a class, the default $orderby value can be specified. When used on properties it can also prevent that property from being referenced in an $orderby OData query option.

• FilterAttributeEdmPropertyConvention Configures the OData $filter query option settings for a type based on the FilterAttribute on the class or on the properties. When used on a class, the default $filter value can be specified. When used on properties it can also prevent that property from being referenced in an $filter OData query option.

• SelectAttributeEdmTypeConvention
  For classes that have SelectAttribute, the attribute will list the properties that can be referenced by the $select OData query option for this structural type.

• SelectAttributeEdmPropertyConvention
  Configures the OData $select query option settings for a type based on the SelectAttribute on the class or on the properties. When used on a class, the default $select value can be specified. When used on properties it can also prevent that property from being referenced in an $select OData query option.

INavigationSourceConvention's

• SelfLinksGenerationConvention
  Generates Item and Edit links in the OData annotations.

• NavigationLinksGenerationConvention
  Generate links without cast for declared and inherited navigation properties, or with a cast in derived types.

• AssociationSetDiscoveryConvention
  This convention adds an association set for each EDM navigation property defined in this type, its base types and all its derived types. The target navigation source chosen is the default navigation source for the navigation property's target entity type. The default navigation source for an entity type is the navigation source that contains entity of that entity type. If more than one navigation source match, the default navigation source is none. If no navigation sources match the default navigation source is the default navigation source of the base type.

IEdmFunctionImportConventions's

• ActionLinkGenerationConvention
  calls action.HasActionLink(..) if the action binds to a single entity and has not previously been configured.

• FunctionLinkGenerationConvention
  calls function.HasFunctionLink(..) if the function binds to a single entity and has not previously been configured.

---

Interesting notes:
I tried to do some research on the history of NotFilterableAttribute vs NonFilterableAttribute but struggled to find a point of divergence in the open source libraries. Both of these attributes exist in the VS 2013 help docs and the System.Web.OData.Query namespace. I assume at one point two different namespaces or libraries were merged together and the attributes were retained for backward compatibility.

What should have happened in the associated commit was that one of these attributes should have been deprecated (annotated with [Obsolete]) and in a future version that deprecated class should have been removed, certainly long before now.

• This same situation exists with NotSortableAttribute and UnsortableAttribute...

Some of these conventions have the same implementation in two different convention classes, one mapped to the Entity Type, the other to the Property. At first glance this looks redundant, but it is necessary for attributes that support both class and property annotation. The reason it is necessary is that the presence of the associated attribute triggers the convention to be evaluated at all. The OData conventions do not operate like the EF code first conventions that evaluate all types and properties for a match. The model is iterated, not the conventions. A class level attribute application, like PageAttribute if we want to allow it to be specified on the property it still needs to apply the logic to the Edm Type. The reverse is try to for FilterAttribute that can be declared once on the Edm Type with an array of properties, or you can manage the properties individually, you might even have both, with property level attributes to explicitly prevent $filter access.

• I can only speculate that someone decided that this was a necessary performance measure as these conventions are evaluated at runtime, we could measure it later if anyone is interested ;)
• For these classes that have multiple similar implementations, I would have designed the logic such that there was a single class that defined the common logic and the concrete types would reference it. This satisfies the DRY principal but also makes the code and patterns like this more discoverable.

Answer 2

The best explanation I'm aware of, is here

Routing Conventions in ASP.NET Web API 2 Odata

NB this is Odata 3, not odata 4

Answer 3

From what I've seen so far, the conventions are those used by Entity Framework, as opposed to any new ones for OData. Please correct me if I am wrong.

More on Code-first conventions, below, but there are many more in the Julie Lerman book I have yet I cannot find an exhaustive list of them on the web.

http://blogs.msdn.com/b/efdesign/archive/2010/06/01/conventions-for-code-first.aspx

Update

The EF modelling conventions system is pluggable and each convention is represented by a class encapsulating the behaviour, and those classes are listed here:

http://msdn.microsoft.com/en-us/library/system.data.entity.modelconfiguration.conventions(v=vs.113).aspx

However that doesn't help with which ones are applicable or used by the ODataConventionModelBuilder if any.

• AssociationInverseDiscoveryConvention - Provides convention to detect navigation properties to be inverses of each other when only one pair of navigation properties exists between the related types.
• AttributeToColumnAnnotationConvention - A general purpose class for Code First conventions that read attributes from .NET properties and generate column annotations based on those attributes.
• AttributeToTableAnnotationConvention - A general purpose class for Code First conventions that read attributes from .NET types and generate table annotations based on those attributes.
• ColumnAttributeConvention - Represents a convention to process instances of ColumnAttribute found on properties in the model.
• ColumnOrderingConvention - Represents a convention to apply column ordering specified via ColumnAttribute or theDbModelBuilder API.
• ColumnOrderingConventionStrict - Convention to apply column ordering specified via ColumnAttribute or theDbModelBuilder API. This convention throws if a duplicate configured column order is detected.
• ComplexTypeAttributeConvention - Represents the convention to process instances of ComplexTypeAttribute found on types in the model.
• ComplexTypeDiscoveryConvention - Represents a convention to configure a type as a complex type if it has no primary key, no mapped base type and no navigation properties.
• ConcurrencyCheckAttributeConvention - Represents the convention to process instances of ConcurrencyCheckAttributefound on properties in the model.
• Convention - A convention that doesn't override configuration.
• DatabaseGeneratedAttributeConvention - Represents a convention to process instances of DatabaseGeneratedAttribute found on properties in the model.
• DecimalPropertyConvention - Convention to set precision to 18 and scale to 2 for decimal properties.
• DeclaredPropertyOrderingConvention - Represents a convention to move primary key properties to appear first.
• ForeignKeyAssociationMultiplicityConvention - Represents a convention to distinguish between optional and required relationships based on CLR nullability of the foreign key property.
• ForeignKeyDiscoveryConvention - Represents a base class for conventions that discover foreign key properties.
• ForeignKeyIndexConvention - Represents a convention to introduce indexes for foreign keys.
• ForeignKeyNavigationPropertyAttributeConvention - Represents a convention to process instances of ForeignKeyAttribute found on navigation properties in the model.
• ForeignKeyPrimitivePropertyAttributeConvention - Represents a convention to process instances of ForeignKeyAttribute found on foreign key properties in the model.
• IdKeyDiscoveryConvention - Convention to detect primary key properties. Recognized naming patterns in order of precedence are: 1. 'Id' 2. [type name]Id Primary key detection is case insensitive.
• IndexAttributeConvention - A convention for discovering IndexAttributeattributes on properties and generatingIndexAnnotation column annotations in the model.
• InversePropertyAttributeConvention - Represents a convention to process instances of InversePropertyAttribute found on properties in the model.
• KeyAttributeConvention - Convention to process instances ofKeyAttribute found on properties in the model.
• KeyDiscoveryConvention - Represents a base class for conventions that discover primary key properties.
• ManyToManyCascadeDeleteConvention - Convention to add a cascade delete to the join table from both tables involved in a many to many relationship.
• MappingInheritedPropertiesSupportConvention - Convention to ensure an invalid/unsupported mapping is not created when mapping inherited properties
• MaxLengthAttributeConvention - Represents a convention to process instances of MaxLengthAttribute found on properties in the model.
• NavigationPropertyNameForeignKeyDiscoveryConvention - Convention to discover foreign key properties whose names are a combination of the dependent navigation property name and the principal type primary key property name(s).
• NotMappedPropertyAttributeConvention - Represents a convention to process instances of NotMappedAttribute found on properties in the model.
• NotMappedTypeAttributeConvention - Represents a convention to process instances of NotMappedAttribute found on types in the model.
• OneToManyCascadeDeleteConvention - Provides a convention to enable cascade delete for any required relationships.
• OneToOneConstraintIntroductionConvention - Provides a convention to configure the primary key(s) of the dependent entity type as foreign key(s) in a one:one relationship.
• PluralizingEntitySetNameConvention - Represents a convention to set the entity set name to be a pluralized version of the entity type name.
• PluralizingTableNameConvention - Represents a convention to set the table name to be a pluralized version of the entity type name.
• PrimaryKeyNameForeignKeyDiscoveryConvention - Convention to discover foreign key properties whose names match the principal type primary key property name(s).
• PrimitivePropertyAttributeConfigurationConvention - Base class for conventions that process CLR attributes found on primitive properties in the model.
• PropertyAttributeConfigurationConvention - Base class for conventions that process CLR attributes found on properties of types in the model.
• PropertyMaxLengthConvention - Represents a convention to set a maximum length for properties whose type supports length facets. The default value is 128.
• RequiredNavigationPropertyAttributeConvention - Convention to process instances ofRequiredAttribute found on navigation properties in the model.
• RequiredPrimitivePropertyAttributeConvention - Represents a convention to process instances of RequiredAttribute found on primitive properties in the model.
• SqlCePropertyMaxLengthConvention - Represents a convention to set a default maximum length of 4000 for properties whose type supports length facets when SqlCe is the provider.
• StoreGeneratedIdentityKeyConvention - Represents a convention to configure integer primary keys to be identity.
• StringLengthAttributeConvention - Represents a convention to process instances of StringLengthAttribute found on properties in the model.
• TableAttributeConvention - Represents a convention to process instances of TableAttribute found on types in the model.
• TimestampAttributeConvention - Represents a convention to process instances of TimestampAttribute found on properties in the model.
• TypeAttributeConfigurationConvention - Base class for conventions that process CLR attributes found in the model.
• TypeNameForeignKeyDiscoveryConvention - Convention to discover foreign key properties whose names are a combination of the principal type name and the principal type primary key property name(s).