title: Why is it Valid to Concatenate Null Strings but not to Call "null.ToString()"?
body: <p>This is valid C# code</p>
  
  <pre><code>var bob = "abc" + null + null + null + "123";  // abc123
  </code></pre>
  
  <p>This is not valid C# code</p>
  
  <pre><code>var wtf = null.ToString(); // compiler error
  </code></pre>
  
  <p>Why is the first statement valid?</p>