As there are various strategies to do this, EF Core providers usually don't set up value generation automatically for date/time columns - you have to configure this yourself. Date/time value generationĪ common request is to have a database column which contains the date/time for when the column was first inserted (value generated on add), or for when it was last updated (value generated on add or update). The SQL Server value generation documentation can be found here. However, specifying ValueGeneratedOnAdd has no effect.Ĭonsult your provider's documentation for the specific value generation techniques it supports. Similarly, byte properties that are configured as generated on add or update and marked as concurrency tokens are set up with the rowversion data type, so that values are automatically generated in the database. However, specifying ValueGeneratedOnAdd on a DateTime property will have no effect ( see the section below for DateTime value generation). Database providers may automatically set up value generation for some property types, but others may require you to manually set up how the value is generated.įor example, on SQL Server, when a GUID property is configured as a primary key, the provider automatically performs value generation client-side, using an algorithm to generate optimal sequential GUID values. Unlike with default values or computed columns, we are not specifying how the values are to be generated that depends on the database provider being used. Protected override void OnModelCreating(ModelBuilder modelBuilder) You can configure any property to have its value generated for inserted entities as follows: We saw above that EF Core automatically sets up value generation for primary keys - but we may want to do the same for non-key properties. Your database provider typically takes care of the necessary configuration for example, a numeric primary key in SQL Server is automatically set up to be an IDENTITY column.įor more information, see the documentation about keys and guidance for specific inheritance mapping strategies. HasComputedColumnSql("LEN() + LEN()", stored: true) īy convention, non-composite primary keys of type short, int, long, or Guid are set up to have values generated for inserted entities if a value isn't provided by the application. You may also specify that a computed column be stored (sometimes called persisted), meaning that it is computed on every update of the row, and is stored on disk alongside regular columns: modelBuilder.Entity() The above creates a virtual computed column, whose value is computed every time it is fetched from the database. On most relational databases, a column can be configured to have its value computed in the database, typically with an expression referring to other columns: modelBuilder.Entity() You can also specify a SQL fragment that is used to calculate the default value: protected override void OnModelCreating(ModelBuilder modelBuilder) You can configure a default value on a property: protected override void OnModelCreating(ModelBuilder modelBuilder) On relational databases, a column can be configured with a default value if a row is inserted without a value for that column, the default value will be used. This page details various patterns for configuration value generation with EF Core. Database columns can have their values generated in various ways: primary key columns are frequently auto-incrementing integers, other columns have default or computed values, etc.
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