title: Unable to determine the relationship represented by navigation 'entitiy' of type 'ICollection<entity>'
body: <p>I am aware of other questions on the same topic, however I have tried their solutions and none have worked for my code.
  I am configuring a one-to-many relationship with one Account with many JoinedClassIds.</p>
  <p><strong>Account.cs</strong></p>
  <pre><code>public class Account {
          // Actual account info
          [Key]
          public int _id { get; set; }
  
          public string _name { get; set; }
          public string _email { get; set; }
  
          public ICollection&lt;JoinedClassId&gt; JoinedClasses { get; set; }
  }
  </code></pre>
  <p><strong>JoinedClassId.cs</strong></p>
  <pre><code>[Keyless]
      public class JoinedClassId {
          public int classIdNumber { get; set; }
          public Account Account { get; set; }
      }
  </code></pre>
  <p><strong>DBContext</strong></p>
  <pre><code>        public DbSet&lt;Account&gt; Accounts { get; set; }
          public DbSet&lt;JoinedClassId&gt; JoinedClassIds { get; set; }
  
          protected override void OnModelCreating(ModelBuilder modelBuilder) {
              modelBuilder.Entity&lt;Account&gt;()
                  .HasMany(acc =&gt; acc.JoinedClasses)
                  .WithOne(jcid =&gt; jcid.Account);
              modelBuilder.Entity&lt;JoinedClassId&gt;()
                  .HasOne(jc =&gt; jc.Account)
                  .WithMany(acc =&gt; acc.JoinedClasses);
              modelBuilder.Entity&lt;JoinedClassId&gt;()
                  .HasNoKey();
          }
  </code></pre>
  <p>I get the error</p>
  <blockquote>
  <p>System.InvalidOperationException: 'Unable to determine the
  relationship represented by navigation 'Account.JoinedClasses' of type
  'ICollection'. Either manually configure the
  relationship, or ignore this property using the '[NotMapped]'
  attribute or by using 'EntityTypeBuilder.Ignore' in
  'OnModelCreating'.'</p>
  </blockquote>
  <p>What can I do to fix this?</p>