Use shadow properties for the key and an alternate key: configuration order matters

[boulc]

I was trying to use shadow properties for the key and an alternate key:

    public class EntityTypeConfiguration : IEntityTypeConfiguration<Entity>
    {
        public void Configure(EntityTypeBuilder<Entity> builder)
        {
            builder.ToTable("Table");

            builder.HasKey("PrimaryKey");
            builder.HasAlternateKey("AdditionalKey");

            builder
                .Property<int>("PrimaryKey") // The name of the shadow property
                .HasColumnName("PK")
                .ValueGeneratedOnAdd()
                .IsRequired();

            builder
                .Property<int>("AdditionalKey") // The name of the shadow property
                .HasColumnName("U")
                .IsRequired();
        }
    }

I got the below exception:

System.InvalidOperationException: The property 'PrimaryKey' cannot be added to the type 'Entity' because there was no property type specified and there is no corresponding CLR property or field. To add a shadow state property the property type must be specified.
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.Property(Type propertyType, String propertyName, MemberInfo memberInfo, Nullable`1 typeConfigurationSource, Nullable`1 configurationSource)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.Property(Type propertyType, String propertyName, Nullable`1 typeConfigurationSource, Nullable`1 configurationSource)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.GetOrCreateProperties(IReadOnlyList`1 propertyNames, Nullable`1 configurationSource, IReadOnlyList`1 referencedProperties, Boolean required, Boolean useDefaultType)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.PrimaryKey(IReadOnlyList`1 propertyNames, ConfigurationSource configurationSource)
   at Microsoft.EntityFrameworkCore.Metadata.Builders.EntityTypeBuilder.HasKey(String[] propertyNames)

Declaring the keys after the properties did the trick, thank to the hint in Relationships - EF Core page:

We recommend explicitly adding the shadow property to the model before using it as a foreign key (as shown below).

Final working code:

    public class EntityTypeConfiguration : IEntityTypeConfiguration<Entity>
    {
        public void Configure(EntityTypeBuilder<Entity> builder)
        {
            builder.ToTable("Table");

            builder
                .Property<int>("PrimaryKey") // The name of the shadow property
                .HasColumnName("PK")
                .ValueGeneratedOnAdd()
                .IsRequired();

            builder
                .Property<int>("AdditionalKey") // The name of the shadow property
                .HasColumnName("U")
                .IsRequired();

            builder.HasKey("PrimaryKey");
            builder.HasAlternateKey("AdditionalKey");
        }
    }

Wouldn't it be worth mentioning that the shadow property to the model must be added before using it as primary or alternate key?

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Document Details

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• ID: 550a3c36-7f1d-efa7-3ed8-769720168da4
• Version Independent ID: 627c4301-e00d-826e-d545-3a244305dec9
• Content: Shadow and Indexer Properties - EF Core
• Content Source: entity-framework/core/modeling/shadow-properties.md
• Product: entity-framework
• Technology: entity-framework-core
• GitHub Login: @AndriySvyryd
• Microsoft Alias: avickers