title: Why .NET String is immutable?
body: <p>As we all know, <a href="http://msdn.microsoft.com/en-us/library/system.string.aspx" rel="noreferrer">String</a> is immutable. What are the reasons for String being immutable and the introduction of <a href="http://msdn.microsoft.com/en-us/library/system.text.stringbuilder.aspx" rel="noreferrer">StringBuilder</a> class as mutable?</p>