Entity Framework Core主键中的引导字符串

Question

I have a problem regarding temporary values in primary keys in EF Core (2.1.4). The value is too long to fit in the database and validation using the DataAnnotations.Validator fails.
If I disable the validator dbcontext.SaveChanges works and handle the value in the correct way.

I have an example table (SQL Server) with this definition:

TestTable
Key1 numeric (18,0)
Key2 char (1) Default value: A

Key1 and Key2 are defined as primary key on the table. Key2 has a default value of A.

This table is reverse engineered in EF Core to this POCO:

public partial class TestTable
{
    [Column(TypeName = "numeric(18, 0)")]
    public decimal Key1 { get; set; }
    [StringLength(1)]
    public string Key2 { get; set; }
}

Note that we are using data annotations on the POCO classes.

The model generated looks like this:

modelBuilder.Entity<TestTable>(entity =>
{
    entity.HasKey(e => new { e.Key1, e.Key2 });
    entity.Property(e => e.Key2)
        .IsUnicode(false)
        .HasDefaultValueSql("('A')");
});

I then add a new item to the dbcontext .

var testTbl = new TestTable { Key1 = 90};
db.TestTable.Add(testTbl);
db.Validate();
db.SaveChanges();

I don't specify Key2 as I want to use the default value from the database.

Before I call Context.SaveChanges() on the dbcontext I would like to validate the entities in the dbcontext. This best way I have found for that until now is:

Public void Validate()
{
    var entities = ChangeTracker.Entries()
    .Where(e => e.State == EntityState.Added || 
    e.State == EntityState.Modified)
    .Select(e => e.Entity)
    .ToList();

    foreach (var entity in entities)
    {
        var vContxt = new ValidationContext(entity);
        List<ValidationResult> validaRes = new List<ValidationResult>();

        if (!Validator.TryValidateObject(entity, validationContext, 
            validationResults, true))
        {
            //Handle validation errors.
        }
    }
}

My problem is that when I add the TestTable object to the dbcontext, Key2 string property automatically get assigned a guid value. When Validate is called it fails because Key2 is not supposed to have a string value longer than 1 character.

If Key2 is not part of the primary key and I remove it from the HasKey method like this:

entity.HasKey(e => new { e.Key1 });

Then Key2 don't get a guid value assigned and the validation works.

Does someone know if there is a way to tell EF Core to not add a guid value to a string value that are part of a key and don't have a value specified? Or is there a way to tell EF Core to obey the data annotation rules defined on the POCO object when assigning a temporary value?

Answer 1

A composite primary key can only be defined by the fluent api.
https://docs.microsoft.com/en-us/ef/core/modeling/keys

Composite keys can only be configured using the Fluent API - conventions will never setup a composite key and you can not use Data Annotations to configure one.

However, you can even use data annotation.
You can use the DatabaseGenerated attribute.
https://docs.microsoft.com/en-us/ef/core/modeling/generated-properties

public partial class TwoKeysTable
{
    public decimal Key1 { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public string Key2 { get; set; }

    public string Test { get; set; }
}

If you want to use fluent api:

entity.Property(e => e.Key2)
         .HasMaxLength(1)
         .HasDefaultValueSql("('A')")
         .ValueGeneratedOnAdd(); // add this