How to fill Foreign Key in a relational database when creating a new row?

Alex Dunlop

I have a model as follows:

[Key]
public int pmId { get; set; }
[Required]
public int pmNumber { get; set; }
[Required]
[MaxLength(50)]
public string costCenter { get; set; }
[Required]
[MaxLength(15)]
public string serviceType { get; set; }
[Required]
[MaxLength(50)]
public string destination { get; set; }
[Required]
[MaxLength(50)]
public string workCenter { get; set; }
[Required]
public DateTime creationDate { get; set; }
[Display]
[Required]
public DateTime startDate { get; set; }
[Required]
public DateTime endDate { get; set; }
[Required]
[MaxLength(100)]
public string mainFileName { get; set; }
public DateTime? returnDate { get; set; }
public string? status { get; set; }
[MaxLength(100)]
public string? fileName { get; set; }
public int? uploader { get; set; }
public bool? isDownloaded { get; set; } = false;

//Navigation property
public virtual AppUser user { get; set; }
//Navigation property
public PM()
{

}

The Foreign Key is id which is Primary Key of the EF Core Identity table. In a form, I need to insert a new row in PM table. I can fill all necessary columns using the following code:

var inputElements = new PM()
{
pmNumber = Convert.ToInt32(adminModel.pmNumber),
costCenter = adminModel.costCenter,
serviceType = adminModel.serviceType,
destination = adminModel.destination,
workCenter = adminModel.workCenter,
creationDate = DateTime.Now,
startDate = DateTime.Now,
endDate = DateTime.Now,
mainFileName = newFileName
};

But, because of relational nature of my tables, I need to specify userId when creating a new row in PM table. How can I set Foreign Key? I can detect userId using Session object but I don't know how to insert it in the table.

Lost User

You have to save the "key" entity; then you can retrieve the generated key. [Retrieve ID of Inserted Entity](https://entityframework.net/retrieve-id-of-inserted-entity)

"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I

Alex Dunlop

I added the following code to PM model:

public int userId { get; set; }

and changed the navigation property to the following code:

//Navigation property
[ForeignKey("userId ")]
public virtual AppUser user { get; set; }