如何在 C# 实体框架核心中使用 class 的构造函数，并将 class 作为字段？

Question

I am just getting started with Entity Framework Core within C#, and I'm trying to set up a class structure where one class has a field that is another class. I have found that, when the classes do not have constructors, the code runs fine. However, when I introduce a constructor as follows:

    public class InterestEF
    {
        public InterestEF(string id, int numTimesInterestSelected, AdminEditEF lastEdit, ICollection<AdminEditEF> allEdits)
        {
            this.id = id;
            this.numTimesInterestSelected = numTimesInterestSelected;
            this.lastEdit = lastEdit;
            this.allEdits = allEdits;
        }

        [Key]
        public string id { get; set; }
        public int numTimesInterestSelected { get; set; }
        public AdminEditEF lastEdit { get; set; }
        public virtual ICollection<AdminEditEF> allEdits { get; set; }
    }

    public class AdminEditEF
    {
        public AdminEditEF(string id, string adminIdEditedBy, DateTime dateEdited, string changesMade, string reasonsForChanges, string idOfEditedEntity, EntityTypeEdited entityTypeEdited)
        {
            this.id = id;
            AdminIdEditedBy = adminIdEditedBy;
            this.dateEdited = dateEdited;
            this.changesMade = changesMade;
            this.reasonsForChanges = reasonsForChanges;
            this.idOfEditedEntity = idOfEditedEntity;
            this.entityTypeEdited = entityTypeEdited;
        }

        [Key]
        public string id { get; set; }
        public string AdminIdEditedBy { get; set; }
        public DateTime dateEdited { get; set; }
        public string changesMade { get; set; }
        public string reasonsForChanges { get; set; }
        public string idOfEditedEntity { get; set; }
        public EntityTypeEdited entityTypeEdited { get; set; }
    }

    public class MySQLEFContext : DbContext
    {
        public DbSet<AdminEditEF> AdminEdits { get; set; }

        public DbSet<InterestEF> interests { get; set; }

        public MySQLEFContext(DbContextOptions<MySQLEFContext> options): base(options) { }

    }

I get the following error:

System.InvalidOperationException: 'No suitable constructor found for entity type 'InterestEF'. The following constructors had parameters that could not be bound to properties of the entity type: cannot bind 'lastEdit' in 'InterestEF(string id, int numTimesInterestSelected, AdminEdit lastEdit)'.'

Basically, I'm just wondering if it's possible to have a class that has classes as fields that also has a set of constructors with parameters I can call elsewhere within code?

Any help would be greatly appreciated. Thank you so much for reading!

Answer 1

From the docs :

• EF Core cannot set navigation properties (such as Blog or Posts above) using a constructor.

So you would need a constructor that looks like this:

public InterestEF(string id, int numTimesInterestSelected)
{
    this.id = id;
    this.numTimesInterestSelected = numTimesInterestSelected;
}

Or a parameterless one:

public InterestEF()
{
}