带有 2 个主键的 C# ASP.NET API Post

Question

I want to use post in a Table where there is 2 primary-keys, and I wanted to do it only using one one of these keys, in that case "classifies.cod_prova". here is the code I've right now:

 [HttpPost]
        public string Post([FromBody] Classifics classifics)
        {
            using (var db = new Dbhelper())
            {
                if (db.classifics.Find(classifics.cod_prova,classifics.cod_cavalo) == null)
                {
                    db.classifics.Add(classifics);
                    db.SaveChanges();
                    return "OK";
                }
                else { return "already exists"; }
            }
        }```

Answer 1

I think you're trying to add a record only if one of the parts of the composite keys doesn't exist in the table for any record. You can't use the Find() method to search for a record that has a composite (2 or more fields) key in the DB using a single field. You could use the .Where() and .Any() methods to find if there are records that contain the one field you're looking for (classifics.cod_prova)

        // This will return true if there are no records that contain the same 
        // value for cod_prova
        if (!db.classifics.Where(c => c.cod_prova == classifics.cod_prova).Any())
        {

            db.classifics.Add(classifics);
            db.SaveChanges();
            return "OK";

        }
        else { return "already exists"; }