title: Compile time error when passing null to a method
body: <p>Is there anyway of avoiding some passing in null into a method.</p>
  
  <p>Something like:</p>
  
  <pre><code>   public static string Add([not null] string word1 , string word2)
          {
              return word1 + word2;
          }
  ![enter image description here][1]
  string sentence = Add(null, "world");
                         ^^ compile error
  </code></pre>