Clarify property/field mapping for read-only properties/fields

[sjb-sjb]

The document explains how to use the NotMapped attribute or the .Ignore fluent method to exclude public properties. How do we include (map) private properites?

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• ID: 76c24b57-557f-a6d6-16f1-1da50e4744cd
• Version Independent ID: 8bee29c6-58e4-1d07-025e-0bdcead9b5a1
• Content: Including & Excluding Properties - EF Core
• Content Source: entity-framework/core/modeling/included-properties.md
• Product: entity-framework
• GitHub Login: @rowanmiller
• Microsoft Alias: divega

[divega]

@sjb-sjb short answer is by using the Property fluent API. But this is obviously missing in the documentation page. Thanks for posting.

[sjb-sjb]

It is worth noting that EF cannot always be informed of collection navigation properties using the Property fluent API. Specifically, the Property method cannot be used to make EF aware of a private navigation whose collection type is a private type derived from ICollection<T>. This is because the Property API does not allow specifying a base class as the type: if you use entityTypeBuilder.Property( typeof(ICollection<T>), propertyName), where the property type is derived from ICollection<T>, then an exception will be thrown saying that the property cannot be added because the property does not have type ICollection<T>. On the other hand if you specify the actual (private) collection type then EF cannot process the type during model construction because it is not a type recognized by EF for navigation collections. The only way to handle this situation, it seems, is to have the collection be public in which case EF notices the ICollection<T> base type and is able to access and use the property.

Also worth noting that specifying the InverseProperty attribute on the navigation collection property does not by itself make the property known to EF.

[Yuant-tobing]

[Bug] Fluent API to exclude a property.

            modelBuilder.Entity<Province>(entity =>
            {
                entity.HasKey(e => e.Iso)
                    .HasName("PK_Province_Iso");

                entity.Ignore(e => e.CountryCodeNavigation);

                entity.Property(e => e.Iso)
                    .HasMaxLength(4)
                    .IsUnicode(false)
                    .IsFixedLength()
                    .ValueGeneratedNever();

                entity.Property(e => e.Name)
                    .IsRequired()
                    .HasMaxLength(80);

                entity.HasOne(e => e.CountryCodeNavigation)
                    .WithMany(e => e.Provinces)
                    .HasForeignKey(e => e.CountryCode)
                    .HasConstraintName("FK_Province_Country_CountryCode")
                    .OnDelete(DeleteBehavior.Restrict);
            });

If I place the script at the top of the entity group, the property still remains in the data response. If I place it at the bottom of the entity group, it will change the DeleteBehavior.Restrict value to DeleteBehavior.Cascade and also not exclude it from the data response.

Migration data.

            migrationBuilder.CreateTable(
                name: "Provinces",
                columns: table => new
                {
                    Iso = table.Column<string>(unicode: false, fixedLength: true, maxLength: 4, nullable: false),
                    Name = table.Column<string>(maxLength: 80, nullable: false),
                    CountryCode = table.Column<short>(nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_Province_Iso", x => x.Iso);
                    table.ForeignKey(
                        name: "FK_Provinces_Countries_CountryCode",
                        column: x => x.CountryCode,
                        principalTable: "Countries",
                        principalColumn: "Code",
                        onDelete: ReferentialAction.Cascade);
                });

[ajcvickers]

@Yuant-tobing Both Ignoring CountryCodeNavigation and later configuring as a navigation is not valid. That is, it's either a navigation or it's ignored--it can't be both.

That being said. this issue tracker is for documentation. If you believe that you're hitting a bug, then please file a new issue at https://github.com/aspnet/EntityFrameworkCore/issues and include a small, runnable project/solution or complete code listing that demonstrates the behavior you are seeing.

[sjb-sjb]

One additional comment on this, I would love to have a PropertyAttribute(string propertyName), because then when I am processing my class definition using T4 I can easily add this attribute if the access is not public. Adding fluent code to the model builder is a lot harder to do using T4.

[sjb-sjb]

Another comment: it seems that a non-public property cannot be used as the Inverse Property for a collection. I would classify it as a bug.

[ajcvickers]

@sjb-sjb If that's the case, that would be a bug. Please file a new issue and post a small, runnable project/solution or complete code listing that demonstrates the behavior you are seeing.

[Danielku15]

short answer is by using the Property fluent API. But this is obviously missing in the documentation page. Thanks for posting.

I would also prefer to have a MappedAttribute like there is a NotMappedAttribute. I mainly try to configure my whole data model via data annotations. Many things seem to be able only via Fluent API which is IMHO not good. Fluent API is EF specific while Data Annotations can be used by multiple frameworks. I'm having an OData API on top of my data model but need to maintain certain things twice because they are "Fluent API" only (like composite keys and cascade delete configurations).

Currently I'm having a class with some properties as explicit interface implementations and cannot tell EF to map them.

[tej-rana]

How do you ignore a non primitive type column? It cannot be mapped as a Property.