title: Unity3D error CS0138 trying to use legacy particle system
body: <p>I am working on a Unity3D project which is trying to use the legacy particle emitter system.</p>
  
  <p>My scripts are failing to compile with error CS0138:</p>
  
  <blockquote>
    <p>Assets/MFPS/Scripts/Weapon/bl_Blast.cs(10,1): error CS0138: A using directive can only be applied to namespaces but UnityEngine.ParticleEmitter denotes a type. Consider using a `using static' instead</p>
  </blockquote>
  
  <p>I am using an asset called "MFPS 1.0.9" and Unity3D version 2018.2.0b9</p>
  
  <p>Here are the <code>using</code> directives at the top of my code:</p>
  
  <pre><code>using UnityEngine;
  using UnityEngine.ParticleEmitter;
  using System.Collections;
  using System.Collections.Generic;
  </code></pre>
  
  <p>I also tried writing that second line as:</p>
  
  <pre><code>using static UnityEngine.ParticleEmitter;
  </code></pre>
  
  <p>That produces a different error:</p>
  
  <blockquote>
    <p>Assets/MFPS/Scripts/Weapon/bl_Blast.cs(10,7): error CS1644: Feature `using static' cannot be used because it is not part of the C# 4.0 language specification </p>
  </blockquote>