ASP.NET Core : Fluent Api relationships configuration

Question

There are a lot of examples how to use Fluent API in the internet, but mostly shows how configure one relationship between two models. In my case I need 3 relationships between 2 models. How to configure relationships between models below with Fluent API?

public class Company
{
    public int Id { get; set; }

    public string Name { get; set; }

    public int FinanceEstimateId { get; set; }
    public Estimate FinanceEstimate { get; set; }

    public int EnvironmentEstimateId { get; set; }
    public Estimate EnvironmentEstimate { get; set; }

    public int SelfEstimateId { get; set; }
    public Estimate SelfEstimate { get; set; }
}

public class Estimate
{
    public int Id { get; set; }
    public string Name { get; set; } // like: bad, good, excellent
    public float Value { get; set; } // like: 1,2,3
}

Answer 1

Maybe this points you in the right direction.

I would go for 2 configurations like:

public class CompanyConfiguration : IEntityTypeConfiguration<Company>
{
    public void Configure(EntityTypeBuilder<Company> builder)
    {
        builder.ToTable("Companies");

        builder
            .HasOne(x => x.EnvironmentEstimate)
            .WithMany()
            .HasForeignKey(x => x.EnvironmentEstimateId)
            .OnDelete(DeleteBehavior.NoAction);

        builder
            .HasOne(x => x.FinanceEstimate)
            .WithMany()
            .HasForeignKey(x => x.FinanceEstimateId)
            .OnDelete(DeleteBehavior.NoAction);

        builder
            .HasOne(x => x.SelfEstimate)
            .WithMany()
            .HasForeignKey(x => x.SelfEstimateId)
            .OnDelete(DeleteBehavior.NoAction);
    }
}

public class EstimateConfiguration : IEntityTypeConfiguration<Estimate>
{
    public void Configure(EntityTypeBuilder<Estimate> builder)
    {
        builder.ToTable("Estimates");
    }
}

You need a DbContext:

public class MyDbContext : DbContext
{
    public DbSet<Company> Companies { get; set; } = null!;

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(@"CONNECTIONSTRING");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        // applies the configuration (those IEntityTypeConfiguration<T> things)
        modelBuilder.ApplyConfigurationsFromAssembly(typeof(MyDbContext).Assembly);
    }
}

I created a console application that demonstrates the usage

using var ctx = new MyDbContext();
await ctx.Database.EnsureDeletedAsync();
await ctx.Database.EnsureCreatedAsync();

var company1 = new Company
{
    Name = "Name1",
    EnvironmentEstimate = new Estimate { Name = "EnvironmentEstimate1", Value = 1 },
    FinanceEstimate = new Estimate { Name = "FinanceEstimate1", Value = 2 },
    SelfEstimate = new Estimate { Name = "SelfEstimate1", Value = 3 }
};

var company2 = new Company
{
    Name = "Name2",
    EnvironmentEstimate = new Estimate { Name = "EnvironmentEstimate2", Value = 4 },
    FinanceEstimate = new Estimate { Name = "FinanceEstimate2", Value = 5 },
    SelfEstimate = new Estimate { Name = "SelfEstimate2", Value = 6 }
};

await ctx.Companies.AddAsync(company1);
await ctx.Companies.AddAsync(company2);
await ctx.SaveChangesAsync();

var result = await ctx.Companies.ToListAsync();

Console.WriteLine("Done");