Using master table key for linking to different table as foreign key in code-first

Question

I've a question using code-first with MVC5. Here's my scenario:

Simple Model

I have LeaveApplication header table which has CompanyCode and WorkGroup fields. And, there's a details table LeaveApplicationDetails which has LeaveTypeCode. Now, LeaveTypes are defined in another model LeaveType, which has Keys {CompanyCode, WorkGroup, LeaveTypeCode}.

Now how I can I link LeaveApplicationDetails model with LeaveType model by using LeaveApplicationHeader model fields in code-first?

Edit: Sample C# code:

public class LeaveTypes
{
    [Key, Column(Order = 0)]
    public int CompCode { get; set; }

    [Key, Column(Order = 1)]
    public int WrkGrp { get; set; }

    [Key, Column(Order = 2)]
    [Required]
    [StringLength(2)]
    public string LeaveTypeCode { get; set; }

    [StringLength(50)]
    public string LeaveTypeName { get; set; }
}

public class LeaveApplicationHeader
{
    [Key]
    public int LeaveAppId { get; set; }

    public int EmpUnqId { get; set; }
    [ForeignKey("EmpUnqId")]
    public Employees Employee { get; set; }

    public int CompCode { get; set; }
    [ForeignKey("CompCode")]
    public Company Company { get; set; }

    public int WrkGrp { get; set; }
    [ForeignKey("CompCode, WrkGrp")]
    public WorkGroups WorkGroup { get; set; }

}


public class LeaveApplicationDetails
{
    [Key, Column(Order = 0)]
    public int LeaveAppId { get; set; }

    [Key, Column(Order = 1)]
    public int LeaveAppItem { get; set; }

    // HOW TO REFER LeaveTypeCode here?
    // Using CompCode and WrkGroup of LeaveApplicationHeader?

}

Answer 1

Now how I can I link LeaveApplicationDetails model with LeaveType model by using LeaveApplicationHeader model fields in code-first?

You can't. For the same reason you can't have a Foreign Key in the database. Either put all of the foreign key columns on one table (eg by making the Key of LeaveApplicationHeader (CompCode ,WrkGrp ,LeaveAppId ), or write a property on LeaveApplicationDetail that queries for the Description as needed.