IT:AD:Code First:DataAnnotations

Important: the use of `DataAnnotations` is not recommended in anything but a POC.

• Domain Entities should be in their own assembly.
• Decorating domain Entities/ with Attributes drag in – and therefore to all assemblies referring to domain entities (ie everywhere) – creates brittle cod e(see: IT:AD:Patterns:Vendors Suck Strategy).
• Prefer the fluent approach: IT:AD:Code First:FluentAPI
  • Not only do they not cause dependencies, but the Fluent approach offers more options.

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# Attributes ##

That said, the most common EF Attributes one can apply are:

• [Key] – Column(s) that define the Primary Key in the database table
• [StringLength] – Minimal and maximal string length (only used for validation purposes not as database constraints)
• [MaxLength] – Can be used instead of [StringLength] to just define the maximal string length of a column
• [ConcurrencyCheck] – Flag that indicates that concurrency checks are activated for the column
• [Required] – Flag that indicates that a value is required for the column (column is flagged as not null)
• [Timestamp] – Flag on time stamp columns which is used for concurrency checks
• [Column] – Specify the name of a column (default property name), can also be used to define the column position
• [Table] – Specify the name of a table (default class name)
• [DatabaseGenerated] – Flag that indicates that the value is filled by the database (possible values are Computed, Identity, None)
• [NotMapped] – Is used to define a property in the class that does not get generated in the database.
• [ForeignKey] and [InverseProperty] – Column(s) that are defined as Foreign Keys

• Annotations
• Override DisplayName
• Relationship between DisplayName and Display
• http://msdn.microsoft.com/en-us/library/system.data.entity.modelconfiguration.conventions(v=vs.103).aspx