Composite Primary key

[DataTowerSystems]

First of all thank you very much for this greate library.
My case is as following:
I have 2 tables (Entities) Product and Category
The product in domain:

public class Product : AuditableEntity, IAggregateRoot
{
public string ProductCode { get; set; } = string.Empty;
public string ProductDescription { get; set; } = string.Empty;
public string ProductCategoryCode { get; set; } = string.Empty;
public Category Category { get; set; } = default!;

[NotMapped]
public string? TenantId { get; set; }

public Product ClearImagePath()
{
    ImagePath = string.Empty;
    return this;
}

}

And the Category in Domain:

public class Category : AuditableEntity, IAggregateRoot
{
public string CategoryCode { get; set; } = string.Empty;
public string CategoryDescriptionArabic { get; set; } = string.Empty;
public string CategoryDescriptionEnglish { get; set; } = string.Empty;
[NotMapped]
public string? TenantId { get; set; }
public ICollection Products { get; set; } = default!;
}

And in Infrastructure/ Persistence/ Configuration
The fluent API

public class CategoryConfig : IEntityTypeConfiguration
{
public void Configure(EntityTypeBuilder builder)
{
builder.IsMultiTenant();

    builder
        .HasIndex(b => new { b.CategoryCode, b.TenantId })
        .IsUnique(true)
        .HasDatabaseName("IX_CategoryCode_TenantId");

    builder
        .Property(b => b.CategoryCode)
        .IsUnicode(false)
        .HasMaxLength(50)
 }

}

public class ProductConfig : IEntityTypeConfiguration
{
public void Configure(EntityTypeBuilder builder)
{
builder.IsMultiTenant();

    builder
    .HasIndex(b => new { b.ProductCode, b.TenantId })
    .IsUnique(true);

   <---- This is the relation between the Product and the Category ------->
      **builder
        .HasOne(b => b.Category)
        .WithMany(b => b.Products)
        .HasForeignKey(b => new { b.ProductCategoryCode, b.TenantId })
        .HasPrincipalKey(b => new { b.CategoryCode, b.TenantId })
        .IsRequired();**
   <---- This is the relation between the Product and the Category ------->
}

}

And this is how it looks in the Database

relations

Until now everything is Ok, the problem is when I create new Category and try to save it I got the following error:
“Unable to track an entity of type 'Category' because alternate key property 'TenantId' is null. If the alternate key is not used in a relationship, then consider using a unique index instead. Unique indexes may contain nulls, while alternate keys may not.”

I hope this is clear now.
Can you please help to solve this issue.
Again Thank you very much for your cooperation.

[AndrewTriesToCode]

Hi! I'm glad you find Finbuckle helpful! I'm at a conference today so I can't give you a full answer until later today, but I will make sure to respond.

[DataTowerSystems]

Hi! I'm glad you find Finbuckle helpful! I'm at a conference today so I can't give you a full answer until later today, but I will make sure to respond.

Thank you very much.

[DataTowerSystems]

Please I am waiting for your answer.
Thank you.

[AndrewTriesToCode]

Do you have a simple repo that shows this problem you can link me to?

Is the error happening when SaveChanges is called or when adding the entity to the dbcontext? Can you shows the code where you are adding the category?

[DataTowerSystems]

I am using this https://github.com/fullstackhero/dotnet-webapi-boilerplate which it use Finbuckle library for Multi tenancy.
This is the saving task in the BaseDbContext class

 public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = new CancellationToken())
    {
        var auditEntries = HandleAuditingBeforeSaveChanges(_currentUser.GetUserId());

        int result = await base.SaveChangesAsync(cancellationToken);

        await HandleAuditingAfterSaveChangesAsync(auditEntries, cancellationToken);

        await SendDomainEventsAsync();

        return result;
    }

The error is when trying to save the row with the Alternate Key says:
"Alternate key can not be null" because the TenantId in that row is null

<---- This is the relation between the Product and the Category ------->
      **builder
        .HasOne(b => b.Category)
        .WithMany(b => b.Products)
        .HasForeignKey(b => new { b.ProductCategoryCode, b.TenantId })
        .HasPrincipalKey(b => new { b.CategoryCode, b.TenantId })
        .IsRequired();**
   <---- This is the relation between the Product and the Category ------->

I hope that I make it clear, thank you very much.

[ashishsinha24]

@DataTowerSystems

Even I am facing the same problem. Did you find a solution for composite keys?

Thanks