摘自http://www.codeproject.com
a struct is implicitly sealed, a class isn't.
a struct can't be abstract, a class can.
a struct can't call : base() in its constructor whereas a class with no explicit base class can.
a struct can't extend another class, a class can.
a struct can't declare protected members (eg fields, nested types) a class can.
a struct can't declare abstract function members, an abstract class can.
a struct can't declare virtual function members, a class can.
a struct can't declare sealed function members, a class can.
a struct can't declare override function members, a class can. The one exception to this rule is that a struct can override the virtual methods of System.Object, viz, Equals(), and GetHashCode(), and ToString().
记得这种区别有在中文网站看过，但这个比较详细点！
