title: C#: SerializableAttribute could not be found
body: <p>I am trying to use the <strong>[Serializable]</strong> attribute in a C# class library project (latest .NET version), but it is <strong>not recognised</strong>. </p>
  
  <p>As far as I could search, Serializable it something that belongs in <s>System.Runtime.Serialization</s> System, but I have used it and it still doesn't work. </p>
  
  <p>I am using it in other projects (Unity), but it doesn't work here. Any ideas?</p>
  
  <pre><code>using System;
  using System.Runtime;
  using System.Xml.Serialization;
  using System.Runtime.Serialization;
  using System.Collections.Generic;
  
  namespace Model{
      [Serializable]
      public struct GameSettings{
          public int Players;
      }
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Ovys6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ovys6.png" alt="The exact error I am getting"></a></p>
  
  <p>Thank you in advance</p>
  
  <p>Edit: format
  Edit2: screenshot of the error</p>