![]() ![]() So, the underlying database generates a value for this column on each insert command, e.g., SQL Server creates an integer IDENTITY column with identity seed and increment to 1.ĮF 6 and EF Core provide the DatabaseGenerated data annotation attribute to configure how the value of a property will be generated. The attribute takes the following DatabaseGeneratedOption enumeration values.Ĭonsider the following example.Next Data Annotations - DatabaseGenerated Attribute in EF 6 & EF CoreĪs you know, EF creates an IDENTITY column in the database for all the id (key) properties of the entity, by default. The DatabaseGenerated attribute specifies how the database generates values for a property. On the navigational property of the principal class, pass the foreign key property name in the dependant class public class Countryįluent API can also be used to set foreign key properties. On the foreign key property of the dependent class, pass the name of the navigation propertyģ. On the navigation property of the dependent class, pass the name of the foreign key property.The foreign key attribute can be applied in 3 ways. It overrides the default naming convention in EF Core for foreign key properties. The ForeignKey attribute is used to specify a foreign key in the relationship between two entities. Here, Order and TypeName parameters are optional. In the above example, the name of the database columns will be DepartmentID and DepartmentName. The Column attribute overrides the default convention where the column name is the same as the property name. The Column attribute is used in an entity class to specify the column name, data type, and column order in a database table. The table's name will be DepartmentMaster even when DbSet property name is different. The following example shows how the Table attribute can be used. It overrides the default convention in EF Core, where the table name is the name of the DbSet property. Table attribute is used to specify the table name in the database and its schema. The following are the schema-related attributes in namespace Table This can be used to specify the maximum length of the corresponding column in the database. This is similar to the MaxLength attribute. The Concurrenc圜heck attribute can be added to any number of properties in an entity class. Entity Framework Core always includes properties with Concurrenc圜heck attribute in where clause of update and delete statements. When the Concurrencycheck attribute is added to a field, it will participate in the where clause of the update statement in Entity Framework Core and throws an error if that field changed after it had been retrieved from the database for modification. When the other one also modifies the record and tries to save it, the first user's changes will be lost, and it will cause data inconsistency. Suppose two users have taken an employee record for modification, and one user saves it after making the changes. Specifies that the corresponding database column participates in optimistic concurrency checks. Timestamp attribute is valid for byte array properties only. It is useful to handle concurrency issues in the database when multiple users simultaneously update the same row. This attribute is used to specify the data type of the corresponding database column as row version. For SQL Server, this will create a nvarchar(250) field in the database. In the following example, the length of the Address property is 250 characters. This can be used to specify the maximum length of the corresponding field in the database. Use this attribute if a database field's value can not be null. Specifies that a property's value is required. In the following example, the key attribute is required to make the EmpId property primary key. The key attribute is required only when no eligible properties are present in the entity class as the primary key by EF Core's convention. ![]() The key attribute can be added to a model property if it is to be used as a primary in the database. The attributes that affect the schema of the database are in namespace. The attributes that generally add constraints to the database columns and the tables are in namespace. ![]() NET provides a set of data annotation attributes that can be used to define constraints to the tables and the columns in the underlying database and override Entity Framework Core conventions. ![]()
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