Mark the EDM model as immutable

Applies To:# OData Web API 8 supported OData Web API v8# OData WebApi v7 for aspnet webapi supported OData AspNet WebApi V7# OData core lib v7 supported OData Core Lib V7

OData libraries at times perform multiple lookups in the EDM model when processing a request. Some of these lookups may be expensive, especially for large models with a lot of schema elements. We have some optimizations in place to reduce the performance overhead of these internal lookups, but some of these optimizations are only applicable if the library knows that the EDM model will not change. You can enable these optimizations by explicitly marking your EDM as immutable by calling the MarkAsImmutable method, which is an extension method in the Microsoft.OData.Edm namespace.

using Microsoft.OData.Edm;

IEdmModel GetEdmModel()
{
    var modelBuilder = new ODataConventionModelBuilder();
    modelBuilder.EntitySet<Person>("People");
    IEdmModel model = modelBuilder.GetEdmModel();
    model.MarkAsImmutable();
    return model;
}

It is recommended to mark the EDM model as immutable since most applications do not modify the model after it has been constructed.

It is however important to note that the library makes no effort to ensure or verify that the model doesn't change after calling this method. It is the responsibility of the developer to ensure that the model is not modified after the MarkAsImmutable method is called. Modifying the model after MarkAsImmutable method has been called may lead to unexpected behavior.

The following code snippet shows an example of incorrect usage of this method:

using Microsoft.OData.Edm;

IEdmModel GetEdmModel()
{
    var model = new EdmModel();
    var personType = new EdmEntityType("Sample.NS", "Person");
    personType.AddKeys(personType.AddStructuralProperty("Id", EdmPrimitiveTypeKind.Int32, isNullable: false));
    model.MarkAsImmutable();

    var addressType = new EdmComplexType("Sample.NS", "Address");
    // DO NOT DO THIS! Modifying the model after calling MarkAsImmutable
    // can lead to unexpected behavior.
    model.AddElement(addressType);
    return model;
}