DATA ANNOTATIONS UPDATE

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 toВ the MaxLength attribute.

The Concurrencењњheck attribute can be added to any number of properties in an entity class.

DATA ANNOTATIONS UPDATE

Entity Framework Core always includes properties with Concurrencењњheck 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.

Data annotations