title: EF Core Mapping EntityTypeConfiguration
body: <p>In EF6 we usually able to use this way to configure the Entity.</p>
  
  <pre><code>public class AccountMap : EntityTypeConfiguration&lt;Account&gt;
  {
      public AccountMap()
      {
          ToTable("Account");
          HasKey(a =&gt; a.Id);
  
          Property(a =&gt; a.Username).HasMaxLength(50);
          Property(a =&gt; a.Email).HasMaxLength(255);
          Property(a =&gt; a.Name).HasMaxLength(255);
      }
  }
  </code></pre>
  
  <p>How we can do in EF Core, since when the class I Inherit EntityTypeConfiguration that unable to find the class.</p>
  
  <p>I download the EF Core raw source code from the GitHub, I can't find it.
  Can someone help on this?</p>