Specifies when the model is used.
The property specifies when the XML model is used.
If the umDesignTime is specified in TEntityModelOptions.Usage, then the meta model becomes accessible at design-time, so properties such as TEntityConnection.DefaultModelName, TEntityContext.ModelName and TEntityTable.TypeName can be configured.
If the umRunTime is specified in TEntityModelOptions.Usage, then the meta model can be used at run-time. For mapping meta model to the entity classes, the special [XmlMapped] class attribute is used. See the XML-mapped entities article for details.