title: SonarQube false positive S1450 for VS 2017 RC C#
body: <p>I think I have found a false positive while using a private readonly variable.
  In the following example I get a warning: <strong>Remove the "_a" field and declare it as a local variable in the relevant method.</strong> <a href="http://www.sonarlint.org/visualstudio/rules/index.html#version=1.22.0.1615&amp;ruleId=S1450" rel="nofollow noreferrer">S1450</a></p>
  
  <pre><code>public class MyClass : MyBaseClass
  {
     private readonly string _a;
  
     public MyClass(string a)
     {
       _a = a;
     }
  
     public override string ToMyString(){
        var test = new MyNewClass(_a);
        return test.MyValue();
     }
  }
  </code></pre>
  
  <p>(ToMyString is acually alot more complex then my above example)</p>
  
  <p>Am I doing something wrong here or is this false positive?</p>
  
  <p>I am using C# .Net Core on VS 2017 RC3 with SonarAnalyzer.CSharp 1.22.0-RC1 </p>