Entity Framework Pitfalls: DbConfiguration Classes Are Automatically Loaded

Entity Framework, since version 6, allows us to specify certain aspects of its configuration by code through a DbConfiguration-derived class. This configuration can be specified in one of three ways:

• A DbConfigurationTypeAttribute when applied to a DbContext class defines the configuration class to be used, if it is not included in the same assembly as the DbContext;
• The codeConfigurationType attribute of the entityFramework section does the same;
• The static SetConfiguration method of the DbConfiguration class can also be used to set the global configuration programmatically.

However, if there is a DbConfiguration-derived class in the same assembly as your DbContext, it will be automatically set as the configuration class, provided that:

• It is public;
• It is non-abstract;
• It has a public parameterless constructor.

So, a DbConfiguration in the same assembly as the DbContext is automatically loaded. If there is more than one, the DbContext constructor will throw an exception.