Configuration

Global Query Filter

• OnModelCreating is a method for defining the model structure:

  • Table mappings
  • Relationships
  • Constraints
  • Default values
  • Query filters ✅

• OnConfiguring is a method for configuring the database connection.

BlogContext.cs

public class BlogContext : DbContext
{
  protected override void OnModelCreating(ModelBuilder modelBuilder)
  {
    modelBuilder.Entity<Blog>()
        .HasQueryFilter(b => !b.IsArchived);
  }
}

To disable it

val allBlogs = await _context.Blogs.IgnoreQueryFilters().ToListAsync();

Save Behaviors

EF Core has two different “phases” of saving: - BeforeSaveBehavior → applies on INSERT - AfterSaveBehavior → applies on UPDATE

1. 🟦 BeforeSaveBehavior (Controls how EF handles the property BEFORE the entity is first saved — INSERT) Options:

   • ✔️ Save ➡️ EF writes the value during INSERT

   • ✔️ Ignore ➡️ EF does not write property value on INSERT

   • ✔️ Throw ➡️ EF throws exception if the property has a value on INSERT ❌ throws InvalidOperationException

2. 🟩 AfterSaveBehavior Controls how EF handles property AFTER the entity is saved — UPDATE) Options:

   • ✔️ Save ➡️ EF updates the value

   • ✔️ Ignore ➡️ EF ignores changes

   • ✔️ Throw ➡️ EF throws exception on modification ❌ throws InvalidOperationException

3. To prevent EF from updating the property after the entity is saved

entity.Code = "ABC123"; context.SaveChanges(); // value written to DB

entity.Code = "XYZ999"; context.SaveChanges(); // ignored — DB value is not updated

builder.Property(p=>p.Code)
    .IsRequired()
    .HasMaxLength(10);

builder.Property(p=>p.Code)
    .Metadata.SetAfterSaveBehavior(PropertySaveBehavior.Ignore); // when the property should be set once and never changed again.