title: Does string concatenation use StringBuilder internally?
body: <p>Three of my coworkers just told me that there's no reason to use a StringBuilder in place of concatenation using the <code>+</code> operator. In other words, this is fine to do with a bunch of strings: <code>myString1 + myString2 + myString3 + myString4 + mySt...</code></p>
  
  <p>The rationale that they used was that since .NET 2, the C# compiler will build the same IL if you use the <code>+</code> operator as if you used a StringBuilder.</p>
  
  <p>This is news to me. Are they correct?</p>