How to use ValueGeneratedOnUpdate() correctly?

How to use ValueGeneratedOnUpdate() correctly?

In Entity Framework Core, the ValueGeneratedOnUpdate() method is used to specify that a property should be updated automatically by the database on an update operation. Here's an example of how to use ValueGeneratedOnUpdate() correctly:

public class MyEntity { public int Id { get; set; } public string Name { get; set; } public DateTime LastModified { get; set; } } public class MyContext : DbContext { public DbSet<MyEntity> MyEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<MyEntity>() .Property(e => e.LastModified) .ValueGeneratedOnUpdate(); } }

In the example above, the MyEntity class has a LastModified property that should be updated automatically by the database on an update operation. The OnModelCreating method is overridden in the MyContext class to configure the LastModified property to be generated on update using the ValueGeneratedOnUpdate() method.

When you save changes to a MyEntity object, the LastModified property will be updated automatically by the database:

using (var context = new MyContext()) { var entity = context.MyEntities.First(); entity.Name = "New Name"; context.SaveChanges(); }

In the example above, the Name property of the MyEntity object is changed and saved to the database using the SaveChanges() method. The LastModified property will be updated automatically by the database.

Note that you should use ValueGeneratedOnUpdate() only for properties that should be updated automatically by the database. If you need to set a property to a specific value on an update operation, you should set the value manually in your code.

Examples

  1. "Entity Framework Core ValueGeneratedOnUpdate example"

    • Description: Learn the basic usage of ValueGeneratedOnUpdate() in Entity Framework Core.
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public DateTime LastUpdated { get; set; } = DateTime.Now; // Set initial value } modelBuilder.Entity<YourEntity>() .Property(e => e.LastUpdated) .ValueGeneratedOnUpdate();

  2. "Entity Framework Core ValueGeneratedOnUpdate with DateTime.UtcNow"

    • Description: Understand how to use ValueGeneratedOnUpdate() with DateTime.UtcNow for accurate timestamp updates.
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public DateTime LastUpdated { get; set; } } modelBuilder.Entity<YourEntity>() .Property(e => e.LastUpdated) .ValueGeneratedOnUpdate() .HasDefaultValueSql("GETUTCDATE()");

  3. "Entity Framework Core ValueGeneratedOnUpdate with Timestamp"

    • Description: Explore using ValueGeneratedOnUpdate() with a timestamp property.
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public byte[] RowVersion { get; set; } } modelBuilder.Entity<YourEntity>() .Property(e => e.RowVersion) .IsRowVersion() .ValueGeneratedOnUpdate();

  4. "Entity Framework Core ValueGeneratedOnUpdate for concurrency"

    • Description: Learn how to use ValueGeneratedOnUpdate() for concurrency control.
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public int Version { get; set; } } modelBuilder.Entity<YourEntity>() .Property(e => e.Version) .ValueGeneratedOnUpdate() .IsConcurrencyToken();

  5. "Entity Framework Core ValueGeneratedOnUpdate for audit trail"

    • Description: Understand how to implement an audit trail using ValueGeneratedOnUpdate().
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public string LastModifiedBy { get; set; } } modelBuilder.Entity<YourEntity>() .Property(e => e.LastModifiedBy) .ValueGeneratedOnUpdate() .HasDefaultValueSql("'System'");

  6. "Entity Framework Core ValueGeneratedOnUpdate with computed column"

    • Description: Explore using ValueGeneratedOnUpdate() with a computed column.
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public int ComputedColumn { get; set; } } modelBuilder.Entity<YourEntity>() .Property(e => e.ComputedColumn) .HasComputedColumnSql("Expression") .ValueGeneratedOnUpdate();

  7. "Entity Framework Core ValueGeneratedOnUpdate with trigger"

    • Description: Learn how to use ValueGeneratedOnUpdate() with a database trigger.
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public int TriggerGeneratedColumn { get; set; } } // Database trigger to update TriggerGeneratedColumn on update

  8. "Entity Framework Core ValueGeneratedOnUpdate with pre-update logic"

    • Description: Understand how to implement pre-update logic with ValueGeneratedOnUpdate().
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public string PreUpdateLogicColumn { get; set; } } // Implement pre-update logic in your service or repository

  9. "Entity Framework Core ValueGeneratedOnUpdate for soft deletes"

    • Description: Explore using ValueGeneratedOnUpdate() for soft delete functionality.
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public bool IsDeleted { get; set; } } modelBuilder.Entity<YourEntity>() .Property(e => e.IsDeleted) .ValueGeneratedOnUpdate() .HasDefaultValue(false);

  10. "Entity Framework Core ValueGeneratedOnUpdate with custom update logic"

    • Description: Learn how to implement custom update logic with ValueGeneratedOnUpdate().
    • Code:
      public class YourEntity { public int Id { get; set; } public string Name { get; set; } public string CustomUpdateColumn { get; set; } } // Implement custom update logic in your service or repository

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