Entity Framework Code-First（9）：DataAnnotations
DataAnnotations in Code-First:
EF Code-First provides a set of DataAnnotation attributes, which you can apply to your domain classes and properties. DataAnnotation attributes override default Code-First conventions.System.ComponentModel.DataAnnotationsincludes attributes that impacts on nullability or size of the column.System.ComponentModel.DataAnnotations.Schemanamespace includes attributes that impacts the schema of the database.
Note:DataAnnotations only give you a subset of configuration options. Fluent API provides a full set of configuration options available in Code-First.
System.ComponentModel.DataAnnotations Attributes:
| Attribute | Description |
|---|---|
| Key | Mark property as EntityKey which will be mapped to PK of the related table. |
| Timestamp | Mark the property as a non-nullable timestamp column in the database. |
| ConcurrencyCheck | ConcurrencyCheck annotation allows you to flag one or more properties to be used for concurrency checking in the database when a user edits or deletes an entity. |
| Required | The Required annotation will force EF (and MVC) to ensure that property has data in it. |
| MinLength | MinLength annotation validates property whether it has minimum length of array or string. |
| MaxLength | MaxLength annotation is the maximum length of property which in turn sets the maximum length of a column in the database |
| StringLength | Specifies the minimum and maximum length of characters that are allowed in a data field. |
System.ComponentModel.DataAnnotations.Schema Attributes:
| Attribute | Description |
|---|---|
| Table | Specify name of the DB table which will be mapped with the class |
| Column | Specify column name and datatype which will be mapped with the property |
| Index | Create an Index for specified column. (EF 6.1 onwards only) |
| ForeignKey | Specify Foreign key property for Navigation property |
| NotMapped | Specify that property will not be mapped with database |
| DatabaseGenerated | DatabaseGenerated attribute specifies that property will be mapped to computed column of the database table. So, the property will be read-only property. It can also be used to map the property to identity column (auto incremental column). |
| InverseProperty | InverseProperty is useful when you have multiple relationships between two classes. |
| ComplexType | Mark the class as complex type in EF. |
Learn about each DataAnnotation attributes in the next sections.
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