The column name 'userid' is specified more than once in the SET clause > or column list of an INSERT

Question

I have recently experienced this error many times, and now again it was raised. Earlier I ended up rewriting almost all of code. Now I am more interested in know why this happens. This is the error:

The column name 'userid' is specified more than once in the SET clause or column list of an INSERT. A column cannot be assigned more than one value in the same clause. Modify the clause to make sure that a column is updated only once. If this statement updates or inserts columns into a view, column aliasing can conceal the duplication in your code.

This is my controller:

[HttpPost]
//[Route("api/Ratings/PostRating/")]
public async Task<ActionResult<Ratings>> PostRating([FromBody] JObject RatingInfo )
{
    
    int id = (int)RatingInfo["id"];
    int val = (int)RatingInfo["val"];
    //Guid userid = Guid.Parse(User.FindFirstValue(ClaimTypes.NameIdentifier));
    //Guid _userid = Guid.Parse("27E72CE4-FC2L-4C18-A27E-974CB4F4448D");
    if (val > 1 || val < 0)
    {
        BadRequest();
    }
    var ratings = await _context.Ratings.FindAsync(id);

    if (ratings == null)
    {
        var newRating = new Ratings();
        //Does not exist
        newRating.Type = "Books";
        newRating.Rating = val;
        newRating.Bookid = id;
        //newRating.Userid = userid;
        _context.Ratings.Add(newRating);
        await _context.SaveChangesAsync();
    }
    else
    {
        //Does exist
        ratings.Active = val;
        _context.Entry(ratings).Property("Active").IsModified = true;


        await _context.SaveChangesAsync();
    }

    return Ok();
    //await _context.SaveChangesAsync();
    //return CreatedAtAction("GetRatings", new { id = ratings.Id }, ratings);
}

What does this error message mean? And why do I get it when I dont even declare userid?

When I have google this problem, rarely they are using Linq/lambda.

EDIT: Because I found the solution in the class, I will paste the original class here too:

public partial class Ratings
{
    public int Id { get; set; }
    public int? Bookid { get; set; }
    public string Type { get; set; }
    public int Rating { get; set; }
    public Guid Userid { get; set; }
    public string Subject { get; set; }
    public DateTime Createdon { get; set; }
    public DateTime? Modifiedon { get; set; }
    public int Active { get; set; }

    public virtual Users User { get; set; }
}

Answer 1

I found the solution. The problem was a related entity, which also had a userid connected. So it was two userids not in the same table, but ef found both. Commenting out the related table solved it.

public partial class Ratings
{
    public int Id { get; set; }
    public int? Bookid { get; set; }
    public string Type { get; set; }
    public int Rating { get; set; }
    public Guid Userid { get; set; }
    public string Subject { get; set; }
    public DateTime Createdon { get; set; }
    public DateTime? Modifiedon { get; set; }
    public int Active { get; set; }

    //public virtual Users User { get; set; }
}